Exhaustion affected residents (9)
I believe the answer is:
tiredness
'exhaustion' is the definition.
(I've seen this before)
'affected residents' is the wordplay.
'affected' is an anagram indicator.
'residents' with letters rearranged gives 'TIREDNESS'.
(Other definitions for tiredness that I've seen before include "Residents in state of fatigue" , "7 (anag)" , "Exhaustion" , "Lassitude; residents (anag.)" , "Weariness" .)