With only this to eat, you'd waste away (7)
I believe the answer is:
fritter
'waste away' is the definition.
'fritter' can be an answer for 'waste' (frittering is a kind of wasting). I'm not sure about the 'away' bit.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for fritter that I've seen before include "Item cooked in batter" , "Something battered and fried" , "Spend money frivolously" , "blow" , "Waste - fried food" .)