Vessel in first half of canal (3)
I believe the answer is:
pan
'vessel' is the definition.
(vessel or container for cooking)
'first half of canal' is the wordplay.
'first half of' means to take half the letters.
'canal' becomes 'panama'.
'panama' cut in half is 'PAN'.
'in' acts as a link.
(Other definitions for pan that I've seen before include "Greek god of flocks and heards" , "cake" , "'Mythical god, half man, half goat (3)'" , "Wash gravel" , "Roast" .)