Discover truth about complaint — not good (6)

I believe the answer is:

rumble

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'discover' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for rumble that I've seen before include "Thunder, perhaps" , "Deep resonant sound - discover an illegal activity" , "gang fight in New York City?" , "Tummy sound - discover (an illicit activity)" , "uncover secrecy perhaps" .)

I've seen this clue in The Times.

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