Crossword Genius

Depression acquired at birth? (9)

Ross

I believe the answer is:

umbilicus

I'm a little stuck... Click here to teach me more about this clue!

This might be a double definition.

'depression' is the first definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'acquired at birth?' is the second definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

Can you help me to learn more?

(Other definitions for umbilicus that I've seen before include "Navel" , "Something in the tummy" .)

I've seen this clue in The Telegraph.
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