I'd pulled up small flower -- catastrophe! (8)
I believe the answer is:
disaster
'catastrophe' is the definition.
('disaster' can be a synonym of 'catastrophe')
'i'd pulled up small flower' is the wordplay.
'pulled up' says the letters should be written backwards.
'small' becomes 's' (abbreviation - e.g. clothes size).
'flower' becomes 'aster' (aster is a kind of flower**).
'id' reversed gives 'di'.
'di'+'s'+'aster'='DISASTER'
(Other definitions for disaster that I've seen before include "Sudden catastrophe" , "Calamity, tragedy" , "Heavy blow" , "Terrible calamity" , "awful situation" .)