Thanks for grand game (3)
I believe the answer is:
tag
'game' is the definition.
(I've seen this before)
'thanks for grand' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'for' is a charade indicator (letters next to each other).
'grand' becomes 'g' ('G' can be a synonym of 'grand'**).
'ta'+'g'='TAG'
(Other definitions for tag that I've seen before include "Tab" , "Name" , "Earmark" , "Label (to attach)" , "Identity badge" .)