Soldier in regiment with pistol raised (7)
I believe the answer is:
regular
'soldier' is the definition.
(member of the regular army)
'regiment with pistol raised' is the wordplay.
'regiment' becomes 'ra' (Royal Artillery).
'with' says to put letters next to each other.
'pistol' becomes 'luger' (I have seen 'German pistol' mean 'luger' so perhaps 'pistol' could also mean 'luger').
'raised' shows that the letters should be reversed in order.
'ra'+'luger'='raluger'
'raluger' back-to-front is 'REGULAR'.
'in' acts as a link.
(Other definitions for regular that I've seen before include "Uniform, even" , "He is a constant patron of 16 Down" , "At set intervals" , "Ordinary" , "Frequent - usual" .)