Crew said something at Chiswick in boat race (4)
I believe the answer is:
Here is my best explanation:
'something at chiswick in boat race' is the definition.
(Chiswick Eyot, island of the Thames)
I don't understand the remainder of the clue.
(Other definitions for eyot that I've seen before include "Islet found in a river, (especially in England)", "Fawlty Towers waiter", "River island", "Small river island", "There's one at Chiswick", "isle", "Island in river", "Little island in a river or lake", "small island" and "land in the river".)