Why chicken didn't cross road: exhausted (3-4)
I believe the answer is:
run-down
I believe this clue is a double definition.
'why chicken didn't cross road' is the first definition.
(as in being run down by a car)
'exhausted' is the second definition.
(I've seen this before)
(Other definitions for run-down that I've seen before include "Dilapidated" , "In a neglected state" , "Exhausted" , "Worn-out" , "Shabby" .)