Atmosphere in centre of clannish Scottish town (5)
I believe the answer is:
nairn
'scottish town' is the definition.
(I've seen this before)
'atmosphere in centre of clannish' is the wordplay.
'atmosphere' becomes 'air' (synonyms).
'in' means one lot of letters goes inside another.
'centre of' means to look at the middle letters.
The central letters of 'clannish' are 'nn'.
'air' inserted within 'nn' is 'NAIRN'.
(Other definitions for nairn that I've seen before include "Scot. Highland town, old county" , "Ran in (anag) - a place in Scotland" , "Scottish Highland resort and port" , "Ran in to the Scottish town" , "Highlander's home" .)