Exhausted river bird found in the street (5)
I believe the answer is:
spent
'exhausted river' is the definition.
'spent' can be an answer for 'exhausted' (I've seen this before). I'm not certain of the 'river' bit.
'bird found in the street' is the wordplay.
'bird' becomes 'pen' (pen is a kind of bird).
'found in' indicates putting letters inside.
'the street' becomes 'st' (abbreviation).
'pen' inserted into 'st' is 'SPENT'.
Can you help me to learn more?
(Other definitions for spent that I've seen before include "Used up; exhausted" , "Exhausted, having paid money?" , "Paid out - finished" , "Worn out - after shopping?" , "Drained of energy - or paid out" .)