Knock about with niece playing card game (8)
I believe the answer is:
patience
'card game' is the definition.
(patience is a kind of card game)
'knock about with niece playing' is the wordplay.
'knock' becomes 'tap' (synonyms).
'about' shows that the letters should be reversed in order.
'with' is a charade indicator (letters next to each other).
'playing' indicates an anagram.
'tap' in reverse letter order is 'pat'.
'niece' anagrammed gives 'ience'.
'pat'+'ience'='PATIENCE'
(Other definitions for patience that I've seen before include "show" , "Musical work" , "there's no one else to play this game" , "G & S' alternative for "Bunthorne''s Bride"" , "Composure" .)