Annoyance when nuance is lost (8)
I believe the answer is:
nuisance
'annoyance' is the definition.
(synonyms)
'nuance is lost' is the wordplay.
'lost' indicates an anagram.
'nuance'+'is'='nuanceis'
'nuanceis' anagrammed gives 'NUISANCE'.
'when' is the link.
(Other definitions for nuisance that I've seen before include "Annoying person/thing" , "Trouble" , "Pest or irritation" , "'Pest, annoyance (8)'" , "Bothersome annoying person" .)