Politeness makes Rosy cute (8)
I believe the answer is:
courtesy
'politeness' is the definition.
(courtesy is a kind of politeness)
'makes rosy cute' is the wordplay.
'makes' indicates an anagram.
'rosy'+'cute'='rosycute'
'rosycute' with letters rearranged gives 'COURTESY'.
(Other definitions for courtesy that I've seen before include "good breeding" , "Civility, politeness" , "Politeness and respect for others" , "Good manners" , "Polite behaviour" .)