Something obnoxious exists to split subtle difference (8)
I believe the answer is:
nuisance
'something obnoxious' is the definition.
I can't tell whether this definition defines the answer.
'exists to split subtle difference' is the wordplay.
'exists' becomes 'is' (if something 'is', it exists).
'to split' is an insertion indicator (some letters split a word into two).
'subtle difference' becomes 'nuance' (I've seen this in another clue).
'is' placed inside 'nuance' is 'NUISANCE'.
Can you help me to learn more?
(Other definitions for nuisance that I've seen before include "Pest, pain in the neck" , "Annoying or troublesome person or thing" , "Irritant or botheration" , "Source of annoyance or aggravation" , "Tiresome person or event" .)