Musical character coming back in duffel coat (4)
I believe the answer is:
clef
'musical character' is the definition.
(I've seen this in another clue)
'coming back in duffel coat' is the wordplay.
'coming back' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'felc' is hidden in the letters of 'duffel coat'.
'felc' backwards is 'CLEF'.
(Other definitions for clef that I've seen before include "Symbol in musical score showing pitch of the notes" , "Treble or bass on a stave" , "Musical key or stave" , "Musical character" , "Treble or bass symbol?" .)