Musical, blooming thing! (5)
I believe the answer is:
I believe this clue is a double definition.
'musical' is the first definition.
(like pop music)
'blooming thing' is the second definition.
(poppy is a kind of flower)
(Other definitions for poppy that I've seen before include "Red field flower" , "catchy records like this" , "Scarlet flower worn in Remembrance" , "Flower of cornfields" , "Girl's name -- scarlet flower" .)