Robin possibly holds first-class foreign capital (7)
I believe the answer is:
nairobi
'foreign capital' is the definition.
(I've seen this before)
'robin possibly holds first-class' is the wordplay.
'possibly' indicates an anagram.
'holds' means one lot of letters goes inside another.
'first class' becomes 'ai' (A1 - top quality).
'robin' is an anagram of 'nrobi'.
'nrobi' going around 'ai' is 'NAIROBI'.
(Other definitions for nairobi that I've seen before include "I, a robin (anag) - city" , "Flat round object" , "Kenyan city" , "Kenyan capital" , "East African capital" .)