Lollapalooza (4)
I believe the answer is:
'lollapalooza' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lulu that I've seen before include "Glaswegian 60s pop singer" , "Berg opera; outstanding thing (colloq.)" , "wonderful thing" , "Berg's unfinished opera" , "beauty" .)