This is a re-occuring endplay theme, and this one is a fairly easy version of it. Win the club ACE (save the king for an all important entry to dummy.
Play two top trumps from your hand, and if necessary, win a thrid on in dummy. Now cash the Three diamonds - discarding a spade - and ruff the last diamond. Now with your carefully protected club King, enter dummy and lead a spade. If your RHO plays a low spade, play the jack (of course if he plays the King or Queen, jump up and win the ACE and continue spades). Note the need to conserve an entry (the club King).
You will find other version of this kind of play right here in the beginner's forum, see... Chamaco's
BBO slams #12 which is a much harder version of a similar concept, or cherdano's
Nice problem seen somewhere else...... If you want to venture out of the BIL section, you might look at
BBO Makable slam #13 which features a similar play as well.
Ben
West North East South
- - - 1♥
Pass 2NT Pass 3♥
Pass 3NT Pass 4♣
Dbl 4♦ Pass 4♠
Pass 4NT Pass 6♥
Pass Pass Pass