Mastered swimming in groups according to ability (8)
I believe the answer is:
streamed
'groups according to ability' is the definition.
I can't tell whether this defines the answer.
'mastered swimming' is the wordplay.
'swimming' indicates anagramming the letters (letters swim around into a new order).
'mastered' anagrammed gives 'STREAMED'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for streamed that I've seen before include "like some chosen schoolchildren?" , "Waved" , "sorted by ability" .)