Italian smoker regularly seen in Estonia (4)
I believe the answer is:
etna
'italian smoker' is the definition.
(I've seen this before)
'regularly seen in estonia' is the wordplay.
'regularly seen in' indicates alternate letters.
The alternate letters of 'estonia' are 'ETNA'.
(Other definitions for etna that I've seen before include "Neat volcano overturned" , "Volcano in Italy" , "It sometimes blows its top" , "Italian volcano" , "Sicilian landmark" .)