Break down when Edward returns to make up (9)
I believe the answer is:
decompose
'break down' is the definition.
(I know that break down can be written as decompose)
'edward returns to make up' is the wordplay.
'edward' becomes 'Ed' (short for Edward).
'returns' shows that the letters should be reversed in order.
'to make up' becomes 'compose' (composing is a kind of making up).
'ed' backwards is 'de'.
'de'+'compose'='DECOMPOSE'
'when' is the link.
(Other definitions for decompose that I've seen before include "Decay, disintegrate" , "as rotters do!" , "Break down" , "Go off" , "Spoil" .)