Vegetable conveys very good impression (7)
I believe the answer is:
opinion
'impression' is the definition.
(I've seen this before)
'vegetable conveys very good' is the wordplay.
I cannot really see how this works, but
'good' could be 'pi' (old-fashioned term for pious) and 'pi' is found within the answer.
'vegetable' could be 'onion' (onion is a vegetable) and 'onion' is found within the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for opinion that I've seen before include "A view held as probable - well, that's mine" , "Personal belief or judgment" , "View, barrister's advice" , "Unproved belief or view" , "Conviction - point of view" .)