Fair or fairly (6)
I believe the answer is:
pretty
'fairly' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for pretty that I've seen before include "Film with Julia Roberts (belle)" , "Reasonably" , "Fair - fairly" , "chocolate-box" , "Pleasing on the eye" .)