Rug from East Estonia is most dull (6)
I believe the answer is:
tamest
'most dull' is the definition.
Both the definition and answer are superlative adjectives. Perhaps there's an association between them I don't understand?
'rug from east estonia' is the wordplay.
'rug' becomes 'mat' (both are floor coverings).
'from east' says the letters should be written backwards.
'estonia' becomes 'est' (I can't explain this - if you can you should believe this answer much more).
'mat' reversed gives 'tam'.
'tam'+'est'='TAMEST'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for tamest that I've seen before include "Meekest or least wild" , "Least wild, most domesticated" , "Most docile" , "Least exciting" , "Most restrained or quiet" .)