Fuss about nothing, principally, arriving from South in principality (7)
I believe the answer is:
andorra
'principality' is the definition.
(I've seen this before)
'fuss about nothing principally arriving from south' is the wordplay.
'fuss' becomes 'ado' (synonyms).
'about' indicates putting letters inside.
'principally' says to take the initial letters.
'arriving' becomes 'arr' (abbreviation used in transport).
'from south' shows that the letters should be reversed in order.
The first letter of 'nothing' is 'n'.
'arr' in reverse letter order is 'rra'.
'ado' placed around 'n' is 'ando'.
'ando'+'rra'='ANDORRA'
'in' acts as a link.
(Other definitions for andorra that I've seen before include "Autonomous principality in the Pyrenees" , "Semi-independent country in Pyrenees" , "Mountainous principality of southwest Europe" , "Independent Pyrenean state" , "Small republic between Spain and France" .)