Theban king about to rip off trousers (5)
I believe the answer is:
Here is my best explanation:
'theban king' is the definition.
(figure of Greek myth)
'about to rip off trousers' is the subsidiary indication.
'about' becomes 're' (regarding**).
'to rip off' becomes 'con' (conning is a kind of ripping off).
'trousers' is an insertion indicator (to trouser can mean to contain or hold).
're' placed inside 'con' is 'creon'.