Set of clothes in case (4)
I believe the answer is:
suit
This clue is a double definition.
'set of clothes' is the first definition.
(I've seen this before)
'case' is the second definition.
('suit' can be a synonym of 'case')
'in' acts as a link.
(Other definitions for suit that I've seen before include "Formal attire" , "Go well with; clothing" , "Become" , "Do as you please!" , "Administrative official" .)