Blue man turned white (7)
I believe the answer is:
albumen
'white' is the definition.
(white of an egg)
'blue man turned' is the wordplay.
'turned' indicates an anagram.
'blue'+'man'='blueman'
'blueman' anagrammed gives 'ALBUMEN'.
(Other definitions for albumen that I've seen before include "Egg-white" , "Egg's white" , "White poacher" , "The white part of an egg" .)