"Chiquitita” quartet (4)
I believe the answer is:
abba
'chiquitita quartet' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for abba that I've seen before include "1970s Swedish pop group" , "Father (used of God in New Testament) - Swedish band" , "rhyme scheme" , "Swedish pop band of the 1970s" , "Bishop" .)