River in twilight? Not quite (5)
I believe the answer is:
indus
'river' is the definition.
(Indus is an example)
'in twilight? not quite' is the wordplay.
'twilight?' becomes 'dusk' ('dusk' can be a synonym of 'twilight').
'not quite' means to remove the last letter.
'dusk' with its final letter removed is 'dus'.
'in'+'dus'='INDUS'
(Other definitions for indus that I've seen before include "River giving its name to an early civilisation" , "Major Asian river" , "River flowing from Tibet to the Arabian Sea" , "Long river of Asia" , "running water" .)