Push a canal boat (5)
I believe the answer is:
barge
This clue is a double definition.
'push' is the first definition.
(I've seen this before)
'a canal boat' is the second definition.
(I've seen this before)
(Other definitions for barge that I've seen before include "Canal boat, towed along (5)" , "Freight-carrying boat" , "force" , "Long, flat-bottomed boat" , "Freight vessel" .)