Calamity as Diana succeeded Daisy (8)
I believe the answer is:
disaster
'calamity' is the definition.
(calamity can mean a disaster)
'diana succeeded daisy' is the wordplay.
'diana' becomes 'di' (Di is short for Diana).
'succeeded' becomes 's' (genealogical abbreviation).
'daisy' becomes 'aster' (I've seen this before).
'di'+'s'+'aster'='DISASTER'
'as' is the link.
(Other definitions for disaster that I've seen before include "Calamity, sudden great misfortune" , "Great tradegy or cataclysm" , "Tragedy of asterids" , "terrible trouble" , "Extreme ruin or misfortune" .)