A robin flying around one city (7)
I believe the answer is:
nairobi
'city' is the definition.
(Nairobi is an example)
'a robin flying around one' is the wordplay.
'flying around' is an anagram indicator.
'one' becomes 'i' (Roman numeral).
'a'+'robin'='arobin'
'arobin' with letters rearranged gives 'nairob'.
'nairob'+'i'='NAIROBI'
(Other definitions for nairobi that I've seen before include "Kenya's capital city" , "I, a robin (anag) - city" , "Flat round object" , "Robinia strangely found in Kenya" , "Kenyan capital" .)