True - defence is never easy it you cannot visualise the tricks needed to beat the contract. The average defender operates within a limited scope of finding alternates. That is so because he has not been groomed to think on the appropriate line, which is the need of the hour.
Sometimes his concentration wavers, at times he misguesses and mostly he misdefends because he is just plain lazy and not attuned to keep a sustained vigil on counting and drawing simple inferences from either partner's discards or signalling and the declarer's particular line of priority in play.
Time and again we present you with problems of defence at bridge to make you realise how important it is in bridge to make counting your habit and then think your way to the best defence strategy. For unless and until you don't fall into the habit of keeping a count of the distribution and points, you would always be groping in the dark, making wild guesses to no avail. Many a contract makes when the defence falters, and gives back the momentum to the declarer to run away with his contract.
Mental laziness is bridge's worst enemy. For it off tracks you from making a list of your priorities and blinds you to the reality. Of course not every hand can give you a key to the perfect count and in many cases, you rely on mere hypothetical count but invariably the bidding, declarer's priority of suit selection in play does give some clue to proper defence. Lets see how you shape up in defence to the problem at hand. The problem in defence can be easy to solve if you are attuned to mental alertness at bridge. First the hand, the bidding and the opening lead. With you sitting as west and holding the following cards with the dummy exposed before you as under after you lead AD.
OPENING LEAD AD.
As you view the dummy, you suddenly look down trodden after leading the AD and finding the KQ of diamonds in dummy giving the added advantage to the declarer who on the bidding is definitely short in diamonds, which means very convenient discards of declarer's losers on the KQ of diamonds. From the bidding you visualise south's distribution to be likely a 6 carder spade along with at least 4 clubs, if not more. If south has 5 clubs, which can be quite likely looking to his 3C jump bid after opening 1S. Well, since south has produced the 2D on your AD, with 5 clubs, he is likely to have 1 heart, which can at most give you 2 tricks.
For then giving south the AKJ XXX spades yielding 8 points you will have to place him with the AC definitely and if not the KC, at least the QC. So with 5 clubs to the AQ, you know you have no chance of beating the contract of 5C for then partner's singleton KC is likely to fall in any case south's jump to 3C definitely places the AC with him and at least 15 to 16 HCP points besides the mammoth distribution of either 6-5 or 6-4.
The critical point of defence has already been reached at trick 2. Your only hope of course lies in placing south with 4 clubs and not 5 to give you a semblance of hope in beating the 5C contract, which on the face of it looks cold.
Sitting west, whats your best defence? Of course you started with the premise that with 5 clubs to the ace, defence has no chance. Even with 4 clubs to the AK, the defence has little chance for declarer can draw trumps in two rounds, leading a heart to the king, which will set up heart king besides KQ of diamonds, the 2 trumps already played and the remaining on a cross ruff. Your only chance lies in partner holding king of clubs doubleton.
Now declarer will need to finesse in clubs for which he needs an immediate entry in dummy. Of course if he has a diamond, his problems are over. If not, declarer has no easy access to dummy for partner with Singleton Spade is over ruffing dummy in spades. Your choice is restricted to spades for you can neither lead a trump nor diamond nor hearts. Simple defence? To lead spades for partner to over ruff later. Are there any snags still? Defence is a careful exercise. Yes, a low spade can be fatal for dummy's 10S could be a key entry. Therefore, you find the killing defence to be QS for declarer held AQJ6 of clubs besides AKJ872 of spades, QX doubleton in hearts with a singleton diamond.

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North      West
10        Q9543
K93         AJ6
KQ64        A98
109742       83
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The Bidding:
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South     West   North    East
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1S          P     1NT        P
3C          P     4C         P
5C                    All pass
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