Rowing crew, we hear, as in the Thames (4)
I believe the answer is:
eyot
'rowing' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for eyot that I've seen before include "isle" , "There's one at Chiswick" , "Little island in a river or lake" , "Fawlty Towers waiter" , "Another term for ait" .)