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' means one lot of letters go next to another.
'playing' indicates anagramming the letters.
'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" .)