An artist having to accept party runs microstate (7)
I believe the answer is:
andorra
'microstate' is the definition.
(I've seen this before)
'an artist having to accept party runs' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'having to accept' means one lot of letters goes inside another.
'party' becomes 'do' (do is a kind of party).
'runs' becomes 'r' (cricket abbreviation).
'an'+'ra'='anra'
'do'+'r'='dor'
'anra' enclosing 'dor' is 'ANDORRA'.
(Other definitions for andorra that I've seen before include "Semi-independent country in Pyrenees" , "Radar on (anag) - European principality" , "Land up, perhaps" , "part of Europe" , "Independent Pyrenean state" .)