In here, there's not just a little drop (5)

I believe the answer is:

abyss

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'in here there's not just a little drop' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

This is the entire clue.

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(Other definitions for abyss that I've seen before include "great depth" , "gaping hole" , "crevasse" , "something rather deep" , "canyon?" .)

I've seen this clue in the Evening Standard.

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