Stick top of oar inside boat (5)
I believe the answer is:
canoe
'boat' is the definition.
(canoe is a kind of boat)
'stick top of oar inside' is the wordplay.
'stick' becomes 'cane' (cane is a kind of stick).
'top of' indicates taking the first letters.
'inside' means one lot of letters goes inside another.
The initial letter of 'oar' is 'o'.
'cane' going around 'o' is 'CANOE'.
(Other definitions for canoe that I've seen before include "Boat one paddles" , "Ocean (anag)" , "Narrow paddle boat" , "Small boat with paddles" , "Boat (that can be dug out!)" .)