N is marked with a club honour by the lead, almost certainly the Q. This gives S a poor 11 count, so he must have some shape. He can't have 6 clubs, playing 3rd and 5th, so presumably 5 clubs and possibly a 4 card major, or maybe 3145. So 3 rounds of clubs, I don't think it matters much if you duck or win the first trick, then cash diamonds. If S follows all the way then either QS or aH honour will drop. If he ruffs a D he has no good exit. If he started with KJxx in H I think you are always going off.