Fairly fair (6)
I believe the answer is:
pretty
'fairly' is the definition.
(I know that fairly can be written as pretty)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pretty that I've seen before include "Moderately" , "chocolate-box" , "sweet" , "Fairly; appealing" , "Rather attractive" .)