"Dancing Queen" singers (4)
I believe the answer is:
'dancing queen singers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for abba that I've seen before include "1970s Swedish pop group" , "Father (NT)" , "group of four stars?" , "Enclosed rhyme" , "Group winning the 1974 Eurovision Song Contest in Brighton" .)