Well on the SQ lead south does well to duck. West can then shift to a club, which south again does well to duck. If a club is continued declarer can win and play a spade. West wins and plays a club, declarer pitches a heart from hand. Declarer can then finesse a diamond and cash his spade pitching a heart from dummy, squeezing RHO out of a heart. Then declarer can duck a heart to east.
West can stop the squeeze by ducking the spade avoiding rectifying the count. Then declarer plays king of hearts, cash a club pitching a spade from hand, 9 of hearts. East covers, declarer wins and plays off 4 rounds of diamonds endplaying east into giving up a heart trick.
So maybe west SHOULDN't have shifted to a club... If he plays ace and a spade east is squeezed at trick 3 (if he pitches a club the same endplay happens). If west plays a low spade at trick 3... declarer can not duck a club into east as west can split. No squeeze or endplay will operate now on east.
So I *think* that queen of spades low spade would set this but maybe running it through deep finesse will give you a better analysis