Knight, despicable type, turned back river (6)

I believe the answer is:

tigris

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'river' is the definition.
(I know that Tigris is a river)

'knight despicable type turned back' is the wordplay.
'knight' becomes 'sir' (a knight has the title Sir).
'despicable type' becomes 'git' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'turned back' is a reversal indicator.
'sir'+'git'='sirgit'
'sirgit' in reverse letter order is 'TIGRIS'.

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(Other definitions for tigris that I've seen before include "Flower of Baghdad" , "Great river flowing from Turkey through Iraq" , "Baghdad's river" , "Great river of 30 across" , "Major tributary of the Euphrates" .)

I've seen this clue in The Guardian.

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