Adamant the one with the gun isn’t breaking out (9)
I believe the answer is:
insistent
'adamant' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?
'one with the gun isn't breaking out' is the wordplay.
'one' becomes 'i' (Roman numeral).
'with' indicates putting letters inside.
'the gun' becomes 'sten' (British sub-machine gun).
'breaking out' indicates anagramming the letters.
'isnt' is an anagram of 'nsit'.
'sten' placed within 'nsit' is 'nsistent'.
'i'+'nsistent'='INSISTENT'
'the' is the link.
Can you help me to learn more?
(Other definitions for insistent that I've seen before include "Not giving up" , "Refusing to be thwarted" , "Demanding attention" , "Determined" , "Unwilling to take "no" for an answer" .)