Intercede with a new composition for spinet (4,2)
I believe the answer is:
step in
'intercede' is the definition.
(I've seen this in another clue)
'a new composition for spinet' is the wordplay.
'spinet' can be anagrammed to 'STEP IN'.
But, I'm not clear how this is indicated.
'with' is the link.
Can you help me to learn more?
(Other definitions for step in that I've seen before include "Intervene dramatically, or at a senior level" , "Substitute" , "Type of garment" , "Interrupt" , "enter" .)