Waves card around at sport (6-7)
I believe the answer is:
roller-skating
'sport' is the definition.
(roller skating is a kind of sport)
'waves card around at' is the wordplay.
I cannot really understand how this works, but
'waves' could be 'rollers' (roller is a kind of wave) and 'rollers' is found in the answer.
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for roller-skating that I've seen before include "Running on wheeled boots" , "sport on wheels" , "Using wheeled boots" .)