The gun that beats the others? (3)
I believe the answer is:
rod
'the gun' is the definition.
(rod is a kind of gun)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for rod that I've seen before include "A few yards" , "Stick - bar" , "Old saying 'Spare the . . . and spoil the child'" , "Staff" , "Bar, shaft" .)