Starchy veg put back in can (3)
I believe the answer is:
may
'can' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for may that I've seen before include "'5 _____' (popular piece of music by Bach)" , "Could" , "The permissive month" , "Has permission" , "plant that's tropical making comeback" .)