Mummy's boy's exploits before work (7)
I believe the answer is:
milksop
'mummy's boy's' is the definition.
(both can mean a timid person)
'exploits before work' is the wordplay.
'exploits' becomes 'milks' (milking is a kind of exploiting).
'before' says to put letters next to each other.
'work' becomes 'op' (common abbreviation for 'opus').
'milks'+'op'='MILKSOP'
(Other definitions for milksop that I've seen before include "Weed" , "Wimpish fellow" , "Weak or effeminate man" , "Feeble male" , "Weakling" .)