Discard song — song intended to be popular (3,5)
I believe the answer is:
lay aside
'discard' is the definition.
(I've seen this before)
'song song intended to be popular' is the wordplay.
I cannot really see how this works, but
'song' could be 'aside' (A-side on a record) and 'aside' is present in the answer.
'popular' could be 'lay' (synonyms) and 'lay' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for lay aside that I've seen before include "Abandon - save for later" , "give up!" , "Abandon - store for future" , "reserve" , "Discard - put by for future use" .)