Unseemly male exploit's beginning behind the scenes (8)
I believe the answer is:
offstage
'behind the scenes' is the definition.
('offstage' can be a synonym of 'behind the scenes')
'unseemly male exploit's beginning' is the wordplay.
'unseemly' becomes 'off' (both can mean unpleasant).
'male' becomes 'stag' (a stag is a male deer**).
'beginning' indicates taking the first letters.
The first letter of 'exploits' is 'e'.
'off'+'stag'+'e'='OFFSTAGE'
(Other definitions for offstage that I've seen before include "out of sight of house" , "No longer acting" , "behind the scenes" , "From the wings of a theatre?" , "not visible from house" .)