Nobbled board-game? Rubbish
I believe the answer is:
got at
'nobbled' is the definition.
(I've seen this before)
'board-game? rubbish' is the wordplay.
'board game?' becomes 'go' (go is a kind of board game).
'rubbish' becomes 'tat' (I've seen this before).
'go'+'tat'='GOT AT'
(Other definitions for got at that I've seen before include "Nobbled" , "Criticised" , "Attacked verbally" , "Unfairly influenced" .)