Uruguayan’s heading race going round and round a small Pacific island (5)
I believe the answer is:
nauru
'small pacific island' is the definition.
(country in the Pacific)
'uruguayan's heading race going round and round a' is the wordplay.
'heading' indicates taking the first letters (head could mean the top letter).
'race' becomes 'run' (synonyms).
'going round' says the letters should be written in reverse.
'and round' is an insertion indicator (some letters go round others).
The first letter of 'uruguayan' is 'u'.
'u'+'run'='urun'
'urun' backwards is 'nuru'.
'nuru' going around 'a' is 'NAURU'.
(Other definitions for nauru that I've seen before include "Fairground carousel" , "SW Pacific republic" , "[OCEANIA] location" , "Small Pacific republic" , "Smallest Pacific state" .)