RAF officer (5,7)
'raf officer' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for wing commander that I've seen before include "UK air force rank" , "Warm end coming (anag.)" , "Air force officer" , "Royal Air Force rank" , "Rank below Gp Capt" .)
(Other definitions for group captain that I've seen before include "do. to colonel" , "RAF rank" , "Officer" , "RAF three Dn" .)