Look on love as a game (3)
I believe the answer is:
loo
'a game' is the definition.
(historical card game)
'look on love' is the wordplay.
'look' becomes 'lo' (archaic exclamation meaning 'look!').
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'love' becomes 'o' (love means zero in tennis).
'lo'+'o'='LOO'
'as' is the link.
(Other definitions for loo that I've seen before include "Ladies, perhaps" , "bog" , "Toilet (informal)" , "In which one goes" , "Lavatory - old card game" .)