Manner of speaking is equal to a weapon (8)
I believe the answer is:
parlance
'manner of speaking' is the definition.
(I've seen this before)
'equal to a weapon' is the wordplay.
'equal' becomes 'par'.
'to a weapon' becomes 'lance' (lance is a kind of weapon).
'par'+'lance'='PARLANCE'
'is' acts as a link.
(Other definitions for parlance that I've seen before include "Earn clap for vocabulary of particular subject" , "Jargon" , "Language" , "Manner of speaking peculiar to a specific group" , "Idiom" .)