A sound boat-race crew, as at Chiswick (4)
I believe the answer is:
eyot
'a sound' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for eyot that I've seen before include "Little island in a river or lake" , "There's one at Chiswick" , "Another term for ait" , "Islet found in a river, (especially in England)" , "land in the river" .)