When this deal cropped up in a training session, some intrepid Souths advanced with two no-trump over two diamonds, and North gambled on a raise.
Take East’s seat now, defending against three no-trump on the lead of the club jack. You should overtake with the queen to unblock the suit. When that holds, continue with the king, ducked again. What now?
Dummy’s diamonds will soon become a threat, so you must set up tricks right away. The auction tells you that the club ace must be on your left, so clearing clubs will achieve nothing since partner has no quick entry. Even if declarer must knock out both of your aces, you will not be able to reach partner.
You must look to the majors, and a spade shift at trick three works only if West has K-x-x. (If he has only a doubleton, declarer could run the shift around to the nine.) A heart switch looks more promising. That just needs partner to have the queen, but the shift must come at trick three while the diamond ace is still in place.
East can up his chances still further by switching to the heart jack. West can hardly have a doubleton here, so this is perfectly safe. This defense generates an extra undertrick if declarer wins with the king, but it also gives the defense a chance when declarer has the heart queen and no 10. Might declarer not duck in hand and duck again on the heart five continuation? He would if he thought East had J-10 (and a doubleton in clubs, since otherwise East would have cleared clubs) and West held the heart ace.