Evidently brilliant swimmer remembers much more than people suspect (8)
I believe the answer is:
goldfish
'remembers much more than people suspect' is the definition.
I can't judge whether this definition defines the answer.
'evidently brilliant swimmer' is the wordplay.
'evidently brilliant' becomes 'gold' (I can't explain this - if you can you should give a lot more credence to this answer).
'swimmer' becomes 'fish' (fish swim).
'gold'+'fish'='GOLDFISH'
Can you help me to learn more?
(Other definitions for goldfish that I've seen before include "Swimmer in a bowl" , "Pond or aquarium fish" , "Domestic pet with an approximate 11-second memory" , "Popular piscine pet" , "Orange-red freshwater fish" .)