Caboose's location (4)
I believe the answer is:
rear
'caboose's location' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rear that I've seen before include "Bring up - back end" , "Bring up (children)" , "early, long before now" , "Raise - back" , "what you may bring up" .)