Dreadful nuisance – I ignored subtle shades (7)
I believe the answer is:
nuances
'subtle shades' is the definition.
(I've seen this before)
'dreadful nuisance i ignored' is the wordplay.
'dreadful' indicates anagramming the letters.
'ignored' is a deletion indicator.
'nuisance' with 'i' taken out is 'nusance'.
'nusance' with letters rearranged gives 'NUANCES'.
(Other definitions for nuances that I've seen before include "Subtle distinctions or variations" , "suggestions" , "Suspicion of" , "subtle shades" , "'Subtle variations, in meaning perhaps (7)'" .)