A grey made brighter (5)
I believe the answer is:
gayer
'brighter' is the definition.
Both the definition and answer are comparative adjectives. Maybe you can see an association between them that I don't see?
'a grey made' is the wordplay.
'made' is an anagram indicator.
'a'+'grey'='agrey'
'agrey' with letters rearranged gives 'GAYER'.
Can you help me to learn more?
(Other definitions for gayer that I've seen before include "More colourful" , "merrier" .)