Group using rhymes in Petrarchan sonnet (4)
I believe the answer is:
abba
I believe this is a double definition.
'group' is the first definition.
(pop group)
'rhymes in petrarchan sonnet' is the second definition.
(I've seen this before)
'using' acts as a link.
(Other definitions for abba that I've seen before include "Swedish pop music group" , "Biblical pop" , "Swedish artists" , "Swedish pop band of the 1970s" , "Palindromic 70s pop group" .)