Rogues serious about theory (5)

I believe the answer is:

guess

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

'rogues serious about' is the wordplay.
'about' indicates a hidden word (the clue goes around or about the answer).
'GUESS' is hidden in the letters of 'rogues serious'.

(Other definitions for guess that I've seen before include "Estimate, supposition" , "Fancy" , "Estimate; suppose" , "Reckon" , "Imagine" .)

I've seen this clue in The Mirror.

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