Good-looking person cutting end off flower -- catastrophe! (8)
I believe the answer is:
disaster
'catastrophe' is the definition.
('disaster' can be a synonym of 'catastrophe')
'good-looking person cutting end off flower' is the wordplay.
'good-looking person' becomes 'dish'.
'cutting end off' means to remove the last letter.
'flower' becomes 'aster' (aster is a kind of flower).
'dish' with its final letter taken away is 'dis'.
'dis'+'aster'='DISASTER'
(Other definitions for disaster that I've seen before include "awful situation" , "Catastrophe, tragedy" , "Terrible calamity" , "Tragedy of asterids" , "Catastrophe, calamity" .)