Footwear in trunk (4)
I believe the answer is:
boot
I believe this clue is a double definition.
'footwear' is the first definition.
(boot is a kind of footwear)
'trunk' is the second definition.
(I know that trunk can be written as boot)
'in' is the link.
(Other definitions for boot that I've seen before include "Kick; footwear" , "They call it a trunk in the US" , "Item of footwear" , "may be packed for a journey" , "eg Wellington" .)