Single male working as wise guy (7)
I believe the answer is:
solomon
'wise guy' is the definition.
(I've seen this before)
'single male working' is the wordplay.
'single' becomes 'solo' (I've seen this before).
'male' becomes 'm' (common abbreviation).
'working' becomes 'on' (on can mean working or activated).
'solo'+'m'+'on'='SOLOMON'
'as' acts as a link.
(Other definitions for solomon that I've seen before include "King known for wisdom" , "Very wise ruler" , "Old king of Israel famous for wisdom and magnificence" , "OT king" , "Wise man" .)