Colour of cream in churn (7)
I believe the answer is:
carmine
'colour' is the definition.
(I know that carmine is a is a more specific form of the action redden)
'cream in churn' is the wordplay.
'churn' is an anagram indicator (I've seen 'churning' mean this).
'cream'+'in'='creamin'
'creamin' with letters rearranged gives 'CARMINE'.
'of' acts as a link.
(Other definitions for carmine that I've seen before include "Bright red" , "Crimson pigment" , "Vivid red colour" .)