Off game: however, consuming duck (3,3)
I believe the answer is:
rub out
'off' is the definition.
(thesaurus)
'game however consuming duck' is the wordplay.
'game' becomes 'RU' (rugby union).
'however' becomes 'but' (I've seen this before).
'consuming' means one lot of letters goes inside another.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'but' enclosing 'o' is 'bout'.
'ru'+'bout'='RUB OUT'
(Other definitions for rub out that I've seen before include "Kill (slang)" , "Delete" , "murder" , "'Erase (3,3)'" , "Erase -- kill" .)