Crossword Genius

As thief may be, and trapeze artist occasionally? (6,2,3,3)

Ross

I believe the answer is:

caught in the act

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'as thief may be' is the definition.
(a thief might be caught in the act of thieving)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for caught in the act that I've seen before include "Clearly guilty" , "as a trapeze artist may be" , "as acrobat might be" , "Obviously responsible" , "Discovered doing something wrong" .)

I've seen this clue in The Times.
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