Old man, artist and soldier (4)
I believe the answer is:
para
'soldier' is the definition.
(short for paratrouper)
'old man artist' is the wordplay.
'old man' becomes 'pa' (both can mean father).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'pa'+'ra'='PARA'
'and' is the link.
(Other definitions for para that I've seen before include "Soldier in an airborne unit" , "Brazilian state" , "High-jumper" , "Soldier who's dropped in? (abbr)" , "Soldier that jumps from planes" .)