Fault that makes me tired (7)
I believe the answer is:
demerit
'fault' is the definition.
(I know that fault can be written as demerit)
'makes me tired' is the wordplay.
'makes' is an anagram indicator.
'me'+'tired'='metired'
'metired' with letters rearranged gives 'DEMERIT'.
'that' is the link.
(Other definitions for demerit that I've seen before include "Fact deserving censure" , "Black mark" , "Feature deserving censure" , "Something deserving censure" , "Conduct that deserves censure" .)