Song in act is put off until later (7)
I believe the answer is:
delayed
'put off until later' is the definition.
I can't tell whether this defines the answer.
'song in act' is the wordplay.
'song' becomes 'lay' (poetic term for a song).
'in' is an insertion indicator.
'act' becomes 'deed' (deed is a kind of act).
'lay' placed inside 'deed' is 'DELAYED'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for delayed that I've seen before include "Shelved" , "Caused to be held up" , "Put back" , "Held up, back" , "Made late" .)