Palindromic pop group (4)
I believe the answer is:
abba
'palindromic pop group' 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 "Form of address to deity" , "famous pop group" , "Group winning the 1974 Eurovision Song Contest in Brighton" , "Biblical pop" , "Bishop" .)