Crossword Genius

Whether or not adjacent to London, it's in Ireland (5)

Ross

I believe the answer is:

derry

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'ireland' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I don't see?

I cannot understand how the rest of the clue works.

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(Other definitions for derry that I've seen before include "Ulster city" , "'The London - - Air' (mus.)" , "Port" .)

I've seen this clue in the Evening Standard.
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