Knowledgeable about weapons and disposed to fight (2,2,4)
I believe the answer is:
up in arms
'knowledgeable' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'weapons and disposed to fight' is the wordplay.
I cannot quite see how this works, but
'weapons' could be 'arms' ('arm' can be a synonym of 'weapon') and 'arms' is located in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'about' is the link.
Can you help me to learn more?
(Other definitions for up in arms that I've seen before include "Protesting hotly" , "Outraged" , "Baby may be" , "Prepared to protest strongly" , "Indignant" .)