Is tango dancing captivating a South American capital? (8)
I believe the answer is:
santiago
'south american capital?' is the definition.
(capital of Chile)
'is tango dancing captivating a' is the wordplay.
'dancing' indicates an anagram.
'captivating' means one lot of letters goes inside another (I've seen this in other clues).
'is'+'tango'='istango'
'istango' anagrammed gives 'sntiago'.
'sntiago' enclosing 'a' is 'SANTIAGO'.
(Other definitions for santiago that I've seen before include "Capital of Chile" , "South American capital" , "Chile's capital" , "Chilean capital" , "City" .)