Kick in the rear? (4)
I believe the answer is:
boot
This clue could be a double definition.
'kick' is the first definition.
(booting is a kind of kicking)
'rear?' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'in the' is the link.
Can you help me to learn more?
(Other definitions for boot that I've seen before include "eg Wellington" , "Heavy footwear" , "Hard kick; part of car" , "Car luggage space; kick" , "Item of footwear" .)