Crossword Genius

Keen fellows put in muscle (6)

Ross

I believe the answer is:

lament

'keen' is the definition.
('lament' can be a synonym of 'keen')

'fellows put in muscle' is the wordplay.
'fellows' becomes 'men' (I've seen this before).
'put in' is an insertion indicator.
'muscle' becomes 'lat' (lat is a kind of muscle).
'men' put into 'lat' is 'LAMENT'.

(Other definitions for lament that I've seen before include "Express sorrow" , "complaint" , "requiem" , "Mourn in mental way (6)" , "Mental (anag)" .)

I've seen this clue in The Independent.
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