Up there, you're in trouble (5)

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 don't understand how they can define each other.

I don't understand the remainder of the clue.

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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