Opponents bid uncontested 1♣-1♥-2♥-4♥-pass.
Your (regular) partner leads a smallish diamond, and there is ♦Q-10 doubleton on the board. You hold one of the missing honours, and declarer obviously holds the ♦A.
Declarer asks your lead style. You reply 3rd & 5th or whatever. "That's not what I meant," he continues. "Is your lead style active or passive?"
Are you obliged to disclose?
Benefits include:
Plus... it's free!