A grave diet, but not all one colour (10)
I believe the answer is:
variegated
'not all one colour' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'a grave diet' is the wordplay.
'a grave diet' anagrams to 'VARIEGATED'.
However, I am not sure how the anagram is indicated.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for variegated that I've seen before include "Showing mixed colours" , "With coloured patches" .)