Naive set off without good food (5,4)
I believe the answer is:
green bean
'food' is the definition.
'naive set off without good' is the wordplay.
'naive' becomes 'green' ('green' can be similar in meaning to 'naive').
'set off' becomes 'began'.
'without' suggests deleting specific letters.
'good' becomes 'g' (abbreviation).
'began' with 'g' removed is 'bean'.
'green'+'bean'='GREEN BEAN'
(Other definitions for green bean that I've seen before include "French" , "Plant" , "Vegetable" , "runner?" .)