"Mamma Mia" band (4)
I believe the answer is:
abba
'mamma mia band' 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" , "rhymes in Petrarchan sonnet" , "Eurovision winners" , "Swedish pop band of the 1970s" , "Coptic bishop's title; Swedish pop group" .)