A nice pet playing game (8)
I believe the answer is:
patience
'game' is the definition.
(I know that patience is a type of card game)
'a nice pet playing' is the wordplay.
'playing' is an anagram indicator.
'a'+'nice'+'pet'='anicepet'
'anicepet' anagrammed gives 'PATIENCE'.
(Other definitions for patience that I've seen before include "that one plays" , "'Forbearance, tolerance (8)'" , "Quality of endurance in operetta" , "Card game for one player" , "Work by G&S" .)