Head of garlic (4)
I believe the answer is:
bulb
'head of garlic' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bulb that I've seen before include "Light fitting" , "Source of flower or light" , "Reproductive organ in some plants" , "Corm; electric light" , "Eg, onion" .)