Make low attack in first RAF exercise (6)
I believe the answer is:
strafe
'make low attack' is the definition.
(attack with low-flying aircraft)
'in first raf exercise' is the wordplay.
'in' indicates a hidden word.
'STRAFE' is hidden within 'first raf exercise'.
(Other definitions for strafe that I've seen before include "Attack with fire from a low-flying plane" , "low attack" , "Shoot at from plane" , "Pepper" , "Attack with fire from aircraft" .)