Onion or shallot, eg (4)
I believe the answer is:
bulb
I believe this is a double definition.
'onion' is the first definition.
(onion is a type of bulb)
'shallot eg' is the second definition.
(shallot is a kind of bulb)
(Other definitions for bulb that I've seen before include "swelling" , "A tulip grows from one" , "shiner" , "Onion, possibly" , "Flower seed or lighting device" .)