Rowing crew (5)
'rowing crew' is the definition.
(crew of eight rowers)
This is all the clue.
(Other definitions for eight that I've seen before include "Number in octet" , "Set of rowers" , "Cardinal number" , "Hit, e.g. (anag.)" , "Number; rowing boat" .)
(Other definitions for sweep that I've seen before include "Raffle" , "Clean with broom" , "range" , "Grimes, say" , "if clean, could result in a whitewash" .)