Enthusiasts choose to enter river and start to swim (8)
I believe the answer is:
devotees
'enthusiasts' is the definition.
(I've seen this in another clue)
'choose to enter river and start to swim' is the wordplay.
I cannot quite understand how this works, but
'choose' could be 'vote' (voting is a kind of choosing) and 'vote' is found within the answer.
'river' could be 'dee' (River Dee) and 'dee' is found in the leftover letters.
A single letter 's' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for devotees that I've seen before include "Fans" , "Ardent followers and admirers" , "Disciples or enthusiasts" .)