Nothing can be seen on English river (4)
I believe the answer is:
nile
'river' is the definition.
(I know that Nile is a river)
'nothing can be seen on english' is the wordplay.
I cannot quite understand how this works, but
'nothing' could be 'nil' (eg nil is zero in football) and 'nil' is found in the answer.
'english' could be 'e' (abbreviation) and 'e' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nile that I've seen before include "Green" , "River that's Blue and White" , "River at Luxor" , "White or Blue river of Africa" , "eastern flower" .)