Soldier in uniform (7)
I believe the answer is:
regular
I believe this clue is a double definition.
'soldier' is the first definition.
(member of the regular army)
'uniform' is the second definition.
(similar in meaning)
'in' is the link.
(Other definitions for regular that I've seen before include "Steady, even" , "Steady, in a fixed order" , "Recurring at short uniform intervals" , "Career soldier" , "Recurring in a uniform manner, say pulse" .)