Venetian boatman making one girl do badly (9)
I believe the answer is:
gondolier
'venetian boatman' is the definition.
(I've seen this before)
'one girl do badly' is the wordplay.
'badly' indicates an anagram (letters in the wrong order).
'one'+'girl'+'do'='onegirldo'
'onegirldo' with letters rearranged gives 'GONDOLIER'.
'making' acts as a link.
(Other definitions for gondolier that I've seen before include "Propeller of Venetian boat" , "Venetian waterworker" , "One to move over water" , "Venetian boater" , "Craftsman" .)