Dreadful nuisance – I ignored subtle shades (7)
I believe the answer is:
Here is my best explanation:
'subtle shades' is the definition.
(I've seen this before)
'dreadful nuisance i ignored' is the wordplay.
'dreadful' indicates an anagram.
'ignored' suggests deleting specific letters.
'nuisance' with 'i' taken away is 'nusance'.
'nusance' with letters rearranged gives 'NUANCES'.