Specialist gets average return in being fascinated (6)
I believe the answer is:
enrapt
'being fascinated' is the definition.
(I've seen this in another clue)
'specialist gets average return' is the wordplay.
'specialist' becomes 'ent' (Ear, Nose and Throat specialist).
'gets' is an insertion indicator (gets can mean captures or absorbs).
'average' becomes 'par' (average score in golf).
'return' shows that the letters should be reversed in order.
'par' written backwards gives 'rap'.
'ent' placed around 'rap' is 'ENRAPT'.
'in' is the link.
(Other definitions for enrapt that I've seen before include "Turned on" , "Deeply absorbed in something" , "Spellbound" , "Sent" , "state of ecstasy" .)