Give gas to member of the clergy (3)
I believe the answer is:
rev
This clue is a double definition.
'give gas to' is the first definition.
(I've seen this in another clue)
'member of the clergy' is the second definition.
(short for reverend)
(Other definitions for rev that I've seen before include "One turn of an engine, in short" , "Motor rotation, in short" , "Increase speed of (an engine)" , "Speed up engine (colloq.)" , "vicar?" .)