Customer for boatman? (6)
I believe the answer is:
punter
I believe this is a double definition.
'customer' is the first definition.
(I've seen this before)
'boatman?' is the second definition.
(thesaurus)
'for' acts as a link.
(Other definitions for punter that I've seen before include "One betting; 4's prey (slang)" , "A colloquial better or a regular client" , "Gambler; customer" , "Better - rugby player - river boatman" , "Person who bets" .)