Little vegetable (3)
I believe the answer is:
pea
'little vegetable' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pea that I've seen before include "Cause of a princess's insomnia?" , "Vegetable in a whistle" , "registered by princess in bed" , "Climber" , "12 in a pod" .)