Place to put picture frame for exhibition -- it's white (7)
I believe the answer is:
albumen
'it's white' is the definition.
(white of an egg)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for albumen that I've seen before include "Egg's white" , "White poacher" , "The white part of an egg" , "Egg-white" .)