A boat you can capsize? (5)
I believe the answer is:
kayak
'a boat' is the definition.
(kayak is a kind of boat)
'you can capsize?' is the wordplay.
I cannot quite understand how this works, but
'you' could be 'ya' (non-standard spelling as in 'see ya later') and 'ya' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for kayak that I've seen before include "Type of canoe" , "Boat used by 23 Across" , "A palindromic canoe for eskimo" , "Inuit canoe" , "Inuit's light canoe" .)