One may get one's hooks into them (4)
I believe the answer is:
eyes
'one' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for eyes that I've seen before include "Looks at carefully" , "Poetically, they're the windows of the soul" , "Closely looks at" , "Narrowly observes" , "Ogles" .)