Insult doesn't start trivial (5)
I believe the answer is:
light
'trivial' is the definition.
(thesaurus)
'insult doesn't start' is the wordplay.
'insult' becomes ''slight' (I've seen this before).
'doesn't start' means to remove the first letter.
'slight' with its initial letter removed is 'LIGHT'.
(Other definitions for light that I've seen before include "Airy; not heavy" , "bulb" , "Blonde" , "Source of illumination" , "Person of authority" .)