Aversion to everything turning grey (7)
I believe the answer is:
allergy
'aversion' is the definition.
(I've seen this before)
'everything turning grey' is the wordplay.
'everything' becomes 'all' (all things).
'turning' indicates anagramming the letters.
'grey' is an anagram of 'ergy'.
'all'+'ergy'='ALLERGY'
'to' is the link.
(Other definitions for allergy that I've seen before include "Antipathy (colloq.)" , "Producer of Hay Fever" , "Cause of ill-feeling" , "Largely to do with adverse reaction" , "Abnormal body reaction" .)