Quick-firing motto (5)
I believe the answer is:
maxim
'motto' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for maxim that I've seen before include "Saw - type of gun" , "Short pithy statement" , "Proverb, aphorism" , "Saying, adage" , "Gorky saw" .)