Soldier picked up artillery weapon (7)
I believe the answer is:
regular
'soldier' is the definition.
(member of the regular army)
'picked up artillery weapon' is the wordplay.
'picked up' is a reversal indicator.
'artillery' becomes 'ra' (Royal Artillery).
'weapon' becomes 'luger' (I've seen this before).
'ra'+'luger'='raluger'
'raluger' backwards is 'REGULAR'.
(Other definitions for regular that I've seen before include "Full-time soldier" , "one often seen at the pub?" , "At set intervals" , "He is a constant patron of 16 Down" , "One present often" .)