As starter for lunch, tucked into game at table (6)
I believe the answer is:
whilst
'as' is the definition.
'starter for lunch tucked into game at table' is the wordplay.
'starter for' indicates taking the first letters (I've seen 'starters for' mean this).
'tucked into' is an insertion indicator.
'game at table' becomes 'whist' (card game played at a table).
The initial letter of 'lunch' is 'l'.
'l' put into 'whist' is 'WHILST'.
(Other definitions for whilst that I've seen before include "As long as; although" , "Whereas" , "At the same time, of old" .)