A few on the river (4)
I believe the answer is:
avon
'the river' is the definition.
(I've seen this before)
'a few on' is the wordplay.
'few' becomes 'v' ().
'a'+'v'+'on'='AVON'
(Other definitions for avon that I've seen before include "Former English county" , "Name of three English rivers" , "Bristol's river" , "River running through Bath" , "River of the Bard" .)