To attack by air may be faster (6)
I believe the answer is:
strafe
'to attack' is the definition.
(to strafe is to attack from the air)
'air may be faster' is the wordplay.
'faster' can be anagrammed to 'STRAFE'.
But, I am not clear how this is indicated.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for strafe that I've seen before include "Rake with machine-gun fire" , "low attack" , "Attack from the air with machine guns" , "Attack with machine-guns from the air" , "Attack with machine guns or cannon from a low-flying plane" .)