The sweetheart of Harlequin in English pantomime (9)
I believe the answer is:
columbine
(Other definitions for columbine that I've seen before include "pantomime character" , "Flower; commedia dell'arte char." , "One with Harlequin, Pierrot, etc" , "Garden flower - Harlequin's partner" , "servant girl in old panto" .)