Your hold: ♠ 962 ♥ 1042 ♦ 543 ♣ KJ54

I would guess to lead the spade two. It is unlikely that a club is standing up, since partner must have at least six and dummy has promised at least three. Also declarer’s jump to slam sounds like he has a void, doesn’t it? With the red suits apparently behaving for declarer, maybe a spade lead will develop at least one trick for your side, but time may be of the essence.