Saint axes Charon’s location (4)

I believe the answer is:

styx

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

'charon's location' is the definition.
I can't judge whether this definition defines the answer.

'saint axes' is the wordplay.
'saint' becomes 'st' (abbreviation).
'axes' becomes 'yx' (Y axis and X axis).
'st'+'yx'='STYX'

Can you help me to learn more?

(Other definitions for styx that I've seen before include "One of the rivers of Hades" , "Underground river" , "River of hell" , "'River of Hate' in Hades" , "Underworld river ferried by Charon" .)

I've seen this clue in The Times.

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