Sister involved with sad calamities (9)
I believe the answer is:
disasters
'calamities' is the definition.
('disaster' can be a synonym of 'calamity')
'sister involved with sad' is the wordplay.
'involved with' indicates an anagram (involved can mean confusing or complex).
'sister' mixed up with 'sad' gives 'DISASTERS'.
(Other definitions for disasters that I've seen before include "Events resulting in great loss and misfortune" , "flops" , "accidents?" .)