Tongue rotten, put away (6,3)
I believe the answer is:
polish off
'put away' is the definition.
(thesaurus)
'tongue rotten' is the wordplay.
'tongue' becomes 'polish' (Polish is an example).
'rotten' becomes 'off' (I've seen this before).
'polish'+'off'='POLISH OFF'
(Other definitions for polish off that I've seen before include "Dispose of" , "defeat" , "Finish completely - kill deliberately" , "Finish (something) quickly" , "Use varnish remover to get this" .)