"Mamma Mia" pop group (4)
I believe the answer is:
abba
'mamma mia pop group' 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 "Father (NT)" , "famous pop group" , "camel-hair coat" , "They used to record" , "Pater's" .)