Lack of interest makes me brood (7)
I believe the answer is:
boredom
'lack of interest' is the definition.
(thesaurus)
'makes me brood' is the wordplay.
'makes' is an anagram indicator.
'me'+'brood'='mebrood'
'mebrood' anagrammed gives 'BOREDOM'.
(Other definitions for boredom that I've seen before include "Feeling" , "Overseers" , "Tedium, ennui" , "Monotony" , "weary idleness" .)