An endless labyrinth over large river (6)

I believe the answer is:

amazon

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

'river' is the definition.
(Amazon is an example)

'an endless labyrinth over large' is the wordplay.
'an' becomes 'a'.
'endless' means to remove the last letter.
'labyrinth' becomes 'maze' (synonyms).
'over large' becomes 'on' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'maze' with its last letter taken away is 'maz'.
'a'+'maz'+'on'='AMAZON'

Can you help me to learn more?

(Other definitions for amazon that I've seen before include "Fighting woman from a great river" , "Strong, well-built woman" , "Great river of S America, or a tough woman" , "Strong woman - large river" , "Mythic woman warrior" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.