They are mostly refined and natural (6)
I believe the answer is:
earthy
'natural' is the definition.
(similar in meaning)
'they are mostly refined' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'refined' is an anagram indicator.
'they'+'are'='theyare'
'theyare' with its last letter removed is 'theyar'.
'theyar' is an anagram of 'EARTHY'.
'and' is the link.
(Other definitions for earthy that I've seen before include "Sensible and practical - crude" , "Unrefined - the ray (anag)" , "Not far removed from nature" , "Coarse or gross" , "Unenthusiastic" .)