Look back and pine for classic song (5)
I believe the answer is:
oldie
'classic song' is the definition.
(I've seen this before)
'look back and pine' is the wordplay.
'look' becomes 'lo'.
'back' is a reversal indicator.
'and' means one lot of letters go next to another.
'pine' becomes 'die' (dying is a kind of pining).
'lo' backwards is 'ol'.
'ol'+'die'='OLDIE'
'for' acts as a link.
(Other definitions for oldie that I've seen before include "Elderly person" , "one who is past it?" , "Publication" , "Perennially popular song or film, often golden" , "The --, UK magazine" .)