It's soft, that is, to eat (3)
I believe the answer is:
pie
'it's soft that is to eat' is the definition.
I can't judge whether this definition defines the answer.
'it's soft that is' is the wordplay.
'it's soft' becomes 'p' (musical abbreviation for 'piano').
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'p'+'ie'='PIE'
Can you help me to learn more?
(Other definitions for pie that I've seen before include "Easy thing" , "Pastry-topped dish" , "Cooked food" , "Confused, mixed type" , "Pecan or blueberry dish?" .)