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' indicates putting letters inside.
'centre of' says to take the centre.
The middle of 'clannish' is 'nn'.
'air' placed inside '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" .)