Daughter is sitting on flower? Catastrophe! (8)
I believe the answer is:
disaster
'catastrophe' is the definition.
(I know that catastrophe can be written as disaster)
'daughter is sitting on flower?' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'sitting on' means one lot of letters go next to another.
'flower?' becomes 'aster' (type of flower).
'd'+'is'+'aster'='DISASTER'
(Other definitions for disaster that I've seen before include "terrible trouble" , "Calamity, tragedy" , "Star dies (anag)" , "awful situation" , "Calamity, sudden great misfortune" .)