Men only put in reduced bid behind the scenes (8)
I believe the answer is:
offstage
'behind the scenes' is the definition.
(synonyms)
'men only put in reduced bid' is the wordplay.
'men only' becomes 'stag' (I've seen this in another clue).
'put in' means one lot of letters goes inside another.
'reduced' means to remove the last letter.
'bid' becomes 'offer' (synonyms).
'offer' with its final letter taken off is 'offe'.
'stag' going inside 'offe' is 'OFFSTAGE'.
(Other definitions for offstage that I've seen before include "behind the scenes" , "out of sight of house" , "Behind-the-scenes" , "From the wings of a theatre?" , "out of sight of the audience" .)