Uniform for a soldier (7)
I believe the answer is:
regular
I believe this clue is a double definition.
'uniform' is the first definition.
('regular' can be similar in meaning to 'uniform')
'a soldier' is the second definition.
(member of the regular army)
'for' acts as a link.
(Other definitions for regular that I've seen before include "Routine" , "In accordance with a fixed order" , "fighter" , "'Steady, uniform (7)'" , "Symmetrically arranged" .)