Plant cultivated for its showy pink or purple flowers whose name derives from its ability to flourish in dry soil (6)
I believe the answer is:
azalea
(Other definitions for azalea that I've seen before include "Showy flowering shrub" , "flower" , "Flowering shrub akin to rhododendron" , "Shrub resembling a small rhododendron" , "Flowering plant akin to rhododendron" .)