Musical number with very little going for it (4)
I believe the answer is:
song
'musical number' is the definition.
(I've seen this in another clue)
'very little going for it' is the wordplay.
'very' becomes 'so' (both can mean 'extremely').
'little' means to remove the last letter (the word is not quite complete).
'going' becomes 'on' (both can mean functioning or activated).
'for' is a charade indicator (letters next to each other).
'it' becomes 'g' (I can't explain this - if you can you should give a lot more credence to this answer).
'so' with its final letter taken away is 's'.
's'+'on'+'g'='SONG'
'with' is the link.
Can you help me to learn more?
(Other definitions for song that I've seen before include "Ballad, aria" , "Ditty" , "You work best when on this" , "Words set to music" , "Piece of vocal music" .)