Pretend to have arrangement that accommodates song (4,3)
I believe the answer is:
play act
'pretend' is the definition.
(I've seen this before)
'arrangement that accommodates song' is the wordplay.
'arrangement' becomes 'pact' (I can't explain this - if you can you should give a lot more credence to this answer).
'that accommodates' is an insertion indicator.
'song' becomes 'lay' (poetic term for a song).
'pact' enclosing 'lay' is 'PLAY-ACT'.
'to have' is the link.
Can you help me to learn more?
(Other definitions for play act that I've seen before include "Work on stage" , "Pretend" , "perform on stage" .)