Fellow holding tune, finally, for a song (5)
I believe the answer is:
cheap
'for a song' is the definition.
(thesaurus)
'fellow holding tune finally' is the wordplay.
'fellow' becomes 'chap' ('chap' can be a synonym of 'fellow'**).
'holding' is an insertion indicator.
'finally' suggests the final letters.
The last letter of 'tune' is 'e'.
'chap' placed around 'e' is 'CHEAP'.
(Other definitions for cheap that I've seen before include "bargain" , "Economical - rubbishy" , "Inexpensive or tasteless" , "Low in price or tastelessly showy" , "Shoddy" .)