Let’s say it’s a green vegetable (7)
I believe the answer is:
lettuce
'a green vegetable' is the definition.
'lettuce' can be an answer for 'vegetable' (lettuce is a kind of vegetable). I am unsure of the 'a green' bit.
'let's say it's' is the wordplay.
'say' becomes 'tuc' (I can't justify this - if you can you should believe this answer much more).
'it' becomes 'e' ('e' can mean 'electronic' which is similar to 'IT').
'let'+'tuc'+'e'='LETTUCE'
Can you help me to learn more?
(Other definitions for lettuce that I've seen before include "Harvest festival item" , "food" , "Leaves eaten in salads" , "Salad stuff" , "Salad leaves" .)