Addled dissenter shows fatigue (9)
I believe the answer is:
tiredness
'fatigue' is the definition.
(synonyms)
'addled dissenter' is the wordplay.
'addled' indicates an anagram.
'dissenter' with letters rearranged gives 'TIREDNESS'.
'shows' acts as a link.
(Other definitions for tiredness that I've seen before include "That's liable to occur at midnight" , "7 (anag)" , "Residents in state of fatigue" , "Weariness" , "Exhaustion" .)