Days on long canal (5)
I believe the answer is:
ditch
'canal' is the definition.
(thesaurus)
'days on long' is the wordplay.
'days' becomes 'd'.
'on' means one lot of letters go next to another.
'long' becomes 'itch' (I've seen this before).
'd'+'itch'='DITCH'
(Other definitions for ditch that I've seen before include "Drop" , "Gully or furrow" , "Drainage channel" , "Abandon - trench" , "Drainage trench" .)