Catastrophes involving policeman’s plants (9)
I believe the answer is:
disasters
'catastrophes' is the definition.
('disaster' can be a synonym of 'catastrophe')
'policeman's plants' is the wordplay.
'policeman's' becomes 'dis' (I've seen this in other clues).
'plants' becomes 'asters' (aster is a kind of plant).
'dis'+'asters'='DISASTERS'
'involving' acts as a link.
(Other definitions for disasters that I've seen before include "accidents?" , "flops" , "Events resulting in great loss and misfortune" .)