Report of discharge in river (4)
I believe the answer is:
ouse
'river' is the definition.
(Yorkshire river)
'report of discharge' is the wordplay.
I cannot quite understand how this works, but
'of' could be 'o' and 'o' is found within the answer.
The remaining letters 'use' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for ouse that I've seen before include "O, Sue, here is a river" , "Name of river in Sussex or Yorkshire" , "River at Bedford" , "River of 1 across" , "Lewes's river" .)