Rowing crew (5)
'rowing crew' is the definition.
(a crew of eight rowers is called an 'eight')
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" .)