Crossword Genius

Up there, you're in trouble (5)

Ross

I believe the answer is:

creek

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

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

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for creek that I've seen before include "Natural stream" , "Rivulet" , "Narrow waterway" , "Small narrow inlet" , "Narrow inlet from the sea" .)

I've seen this clue in the Evening Standard.
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