Remove their guns, OK? (4,5)
I believe the answer is:
sure thing
'ok?' is the definition.
(thesaurus)
'remove their guns' is the wordplay.
'remove' indicates an anagram (move the letters again).
'their'+'guns'='theirguns'
'theirguns' anagrammed gives 'SURE THING'.
(Other definitions for sure thing that I've seen before include "of course" , "no chance of losing" , "A certainty - I agree!" , "cert" .)