Canal and river boats (6)
I believe the answer is:
barges
'canal and river boats' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for barges that I've seen before include "Broad flat-bottomed boats" , "Moves clumsily in canal boats" , "Flat-bottomed boats for carrying loads" , "Inland waterway boats" , "Inland water vessels" .)