Convincing maxim about dizzy fits (10)
I believe the answer is:
satisfying
'convincing' is the definition.
(thesaurus)
'maxim about dizzy fits' is the wordplay.
'maxim' becomes 'saying' (I've seen this in another clue).
'about' is an insertion indicator.
'dizzy' is an anagram indicator.
'fits' anagrammed gives 'tisf'.
'saying' going around 'tisf' is 'SATISFYING'.
(Other definitions for satisfying that I've seen before include "Fulfilling (a need)" , "enough?" , "Cool" , "Meeting (requirements)" , "Pleasurable" .)