Crossword Genius

Sibling separated from dysfunctional parent, finally understood (4)

Ross

I believe the answer is:

kent

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'sibling' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for kent that I've seen before include "English architect and landscape gardener" , "Part of 1 25 [KING LEAR]" , "County of SE England" , "Southern English county" , "known in Scotland" .)

I've seen this clue in The Guardian.
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