Who flogs beer on board? One on board (8)
I believe the answer is:
salesman
'who flogs' is the definition.
'beer on board? one on board' is the wordplay.
'beer' becomes 'ale' (I've seen this before).
'on' indicates putting letters inside.
'board?' becomes 'ss' (I've seen this in other clues**).
'one on board' becomes 'man' (term for a chess piece).
'ale' placed within 'ss' is 'sales'.
'sales'+'man'='SALESMAN'
(Other definitions for salesman that I've seen before include "He sells strange lean mass" , "He sells goods and services" , "Death of a . . . . . . . . (Arthur Miller) (8)" , "He sells lean mass, oddly" , "Company representative" .)