Most balanced article written in small refuge (6)
I believe the answer is:
sanest
'most balanced' is the definition.
'article written in small refuge' is the wordplay.
'article' becomes 'a' (example of the part-of-speech).
'written in' means one lot of letters goes inside another.
'small' becomes 's' (abbreviation - e.g. clothes size).
'refuge' becomes 'nest'.
's'+'nest'='snest'
'a' going inside 'snest' is 'SANEST'.
(Other definitions for sanest that I've seen before include "Most rational and reasonable" , "Most rational and logical" , "Most sensible" , "Assent, being most rational" , "Mentally most healthy" .)