Vegetable has one on both sides (5)
I believe the answer is:
onion
'vegetable' is the definition.
(onion is a vegetable)
'one on both sides' is the wordplay.
'both sides' becomes 'ion' (I can't explain this - if you can you should give a lot more credence to this answer).
'on'+'ion'='ONION'
'has' is the link.
Can you help me to learn more?
(Other definitions for onion that I've seen before include "Shape of Russian dome" , "One may be set" , "Pungent vegetable" , "Edible tear-jerker" , "Bulb used as a vegetable" .)