Stick fences in for dog, say (6)
I believe the answer is:
canine
'dog say' is the definition.
(dog is a kind of canine)
'stick fences in' is the wordplay.
'stick' becomes 'cane' (cane is a kind of stick).
'fences' becomes 'ni' (I am not sure about this - if you are sure you should believe this answer much more).
'in' means one lot of letters goes inside another.
'cane' going around 'ni' is 'CANINE'.
'for' is the link.
Can you help me to learn more?
(Other definitions for canine that I've seen before include "Pointed conical tooth" , "Of or like dogs" , "A tooth; of our best friend" , "Tooth; dog" , "like a setter" .)