Favouring some show of force? (3)
I believe the answer is:
for
'favouring' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for for that I've seen before include "Favouring" , "Pro" , "Approving" , "See 24" , "On the side of" .)