Wrong done with gun in prison cell (7)
I believe the answer is:
dungeon
'prison cell' is the definition.
(I've seen this before)
'wrong done with gun' is the wordplay.
'wrong' is an anagram indicator.
'with' says to put letters next to each other.
'done' after 'gun' is 'gundone'.
'gundone' with letters rearranged gives 'DUNGEON'.
'in' acts as a link.
(Other definitions for dungeon that I've seen before include "Dark place of confinement" , "Place of confinement underground" , "Eg, the Black Hole of Calcutta" , "Keep" , "part of prison" .)