The NT is 12-14 and the 2C is Stayman. South's 2D is a suit. The 3C bid is not forcing, but shows at least 5 clubs, 4 spades (because of Stayman) and 11-12 points. North leads the S6.
Declarer is pleased diamonds are not led, which would have meant the contract would likely be 1 off.
There are two possibilities for making the contract.
(a) Duck the spade. If South does not have the S10, he will probably play the K or Q. South will subsequently gain the lead with the DK (South is likely to have the DA) or a heart, and finesse the SJ for 9 tricks - 2 spades, 6 clubs and 1 red suit trick.
(b) Win the SA, cash 6 clubs and lead a heart to the HK. Declarer can reason as follows. South is assumed to have the DA, since surely North would have led a diamond if he held the ace of partner's lead-directing bid. South cannot have more than 3 spades and probably has one of the missing top honour. Hence, since the only possible entries for North are the HA and a top spade honour, the SJ should prevent the loss of 3 spade tricks. The 8th trick will be a heart and the 9th should be the SJ or the DK. Declarer can discard 2 diamonds and a heart on the long clubs, but either or both the defenders may have difficult decisions on discards. If the HK wins, Declarer will obviously play South for the HA and will now need to duck a spade, expecting to come to a 9th trick in the end game. (Hence it is important for Declarer not to discard his last spade.)
On the actual hand, North has the HA, and will probably win the HK and lead a spade, won by South's SK. South will cash the DA and return the HJ, his last heart. Assuming that the H9 is still out, Declarer has to decide who holds it. If South, The heart must be won and a heart returned. If North, then the heart must be ducked. The discards will probably indicate the likely distribution.