Canal and river boats (6)
I believe the answer is:
barges
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">canal and river boats</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)