Denied any necessity to possess a gun (7)
I believe the answer is:
negated
'denied' is the definition.
(I've seen this before)
'any necessity to possess a gun' is the wordplay.
'any necessity' becomes 'need' (synonyms. I am not sure about the 'any' bit.).
'to possess' means one lot of letters goes inside another.
'a gun' becomes 'gat' (gat is a kind of gun).
'need' placed around 'gat' is 'NEGATED'.
Can you help me to learn more?
(Other definitions for negated that I've seen before include "Made ineffective" , "Nullified" , "Abrogated" , "Contradicted" , "Cancelled or destroyed the effect of something" .)