Painting, crouch so air can circulate (11)
I believe the answer is:
chiaroscuro
'painting' is the definition.
(I've seen this before)
'crouch so air can circulate' is the wordplay.
'can circulate' indicates an anagram.
'crouch'+'so'+'air'='crouchsoair'
'crouchsoair' with letters rearranged gives 'CHIAROSCURO'.
(Other definitions for chiaroscuro that I've seen before include "Caruso choir (anag) - light and shade" , "Black and white" , "Monochrome" , "light and dark in painting" , "contrast in painting" .)