Plant, initially from Umbria, cultivated here shows impressive adaptability (7)
I believe the answer is:
fuchsia
'plant' is the definition.
(type of shrub)
'initially from umbria cultivated here shows impressive adaptability' is the wordplay.
'initially' says to take the initial letters.
The initial letters of 'from umbria cultivated here shows impressive adaptability' is 'FUCHSIA'.
(Other definitions for fuchsia that I've seen before include "Shrub with pendulous purplish-red flowers" , "Bush" , "Ornamental flowering plant - reddish-purple" , "Flowering shrub" , "One blooming" .)