You are defending; if partner asks you to lead a particular suit, do so — unless you are absolutely certain it is better to lead a different suit.
In today’s deal, East’s decision not to open, but to overcall at the three-level, was dubious. It is safer to open a borderline hand than to overcall later, especially at such a high level, because the opponents are much more likely to produce a lucrative penalty double at the higher level. Here, though, South could hardly pass over three clubs.
West led the club ace and switched to the heart 10: six, queen, jack. East returned the club eight, the high spot being intended as a suit-preference signal for hearts. After ruffing, though, West shifted to a diamond. He knew, from the appearance of the heart jack, that a heart return would be ruffed by South.
Declarer won with dummy’s king and called for a low spade. Here, East made the correct move: He went up with the spade ace. But then he made an error: He tried to cash the heart ace. He was annoyed that his partner hadn’t led a heart at trick four. Declarer ruffed, drew the remaining trumps with the spade king and claimed. If only East had led another club, West’s spade queen would have been promoted as the setting trick.
East was clearly wrong, but suppose West leads a heart regardless at trick four. Declarer ruffs, plays a diamond to the dummy and calls for a spade. Now East can win with his ace and lead a club, effecting a trump promotion. So West was wrong also!