Well versed in guns, is peeved (2,2,4)
I believe the answer is:
up in arms
'guns is peeved' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'well versed in' is the wordplay.
I cannot really understand how this works, but
'in' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for up in arms that I've seen before include "Weapons expert should be" , "Prepared to protest strongly" , "Involved in protest" , "held like a small child" , "Young child may be found here" .)