The super with the gun is outside again (5)
I believe the answer is:
great
'the super' is the definition.
(I've seen this in another clue)
'gun is outside again' is the wordplay.
'gun' becomes 'gat' (US informal term for a gun).
'is outside' means one lot of letters goes inside another (some letters go outside others).
'again' becomes 're' (prefix meaning 'again').
'gat' going around 're' is 'GREAT'.
'with the' is the link.
(Other definitions for great that I've seen before include "Large, important" , "Very large in size, quantity, etc." , "Large, outstanding" , "Of major significance - very good" , "Wonderful" .)