Can be a goat (5)
I believe the answer is:
billy
I believe this is a double definition.
'can' is the first definition.
(I've seen this before)
'a goat' is the second definition.
(billy is a kind of goat)
'be' is the link.
(Other definitions for billy that I've seen before include "Light metal cooking pot used for camping" , "Cooking can for William" , "Camp can" , "Metal camping can for tea" , "Goat; camper's kettle" .)