Topless chap having 45 mins with mature escort (9)
I believe the answer is:
entourage
'escort' is the definition.
(thesaurus)
'topless chap having 45 mins with mature' is the wordplay.
'topless chap' becomes 'ent' (I can't justify this - if you can you should believe this answer much more).
'having' says to put letters next to each other.
'45 mins' becomes 'our' (ie 'three quarters' of the word 'hour').
'with' is a charade indicator (letters next to each other).
'mature' becomes 'age' (synonyms).
'ent'+'our'+'age'='ENTOURAGE'
(Other definitions for entourage that I've seen before include "Support team" , "Group of attendants" , "Ego nature found in accompanying group" , "Group of followers" , "company" .)