I guess your system is a strong club with a strong NT? Partner must have
♦54, because he would play the 5 with 542. Looks like he is 3424. Given that he led from at most
♥KJxx, he must have the
♣A. I duck, win the second diamond and play a club. Partner wins and keeps plugging away at
♣, then declarer has to lead hearts for himself, just in case he has
♥AJxx. Declarer will probably advance the
♥9 when on table after the first diamond so I'll cover and partner can put me with the
♦A to play clubs. Declarer has misplayed so we should be in for a fine score anyway.
By the way, I always try to get the best score possible