Enthusiast left to rove about (5)
I believe the answer is:
lover
'enthusiast' is the definition.
(thesaurus)
'left to rove about' is the wordplay.
'left' becomes 'l' (common abbreviation).
'about' indicates anagramming the letters.
'rove' anagrammed gives 'over'.
'l'+'over'='LOVER'
(Other definitions for lover that I've seen before include "Boyfriend" , "Sweetheart" , "Devotee" , "Suitor" , "toy boy" .)