As dessert, sounds very good (3)
I believe the answer is:
pie
'as dessert' is the definition.
I can't tell whether this definition defines the answer.
'sounds very good' is the wordplay.
'sounds' indicates a 'sounds like' (homophone) clue.
'very good' becomes 'pi' (old-fashioned slang for pious).
'pi' sounds like 'PIE'.
Can you help me to learn more?
(Other definitions for pie that I've seen before include "Irrational things to do with circles and logs" , "what to cook for dinner?" , "In the sky, it's an empty promise" , "Covered flan" , "See 6" .)