Whale trapped in major catastrophe (4)
I believe the answer is:
orca
'whale' is the definition.
(orca is a kind of whale)
'trapped in major catastrophe' is the wordplay.
'trapped in' indicates a hidden word.
'ORCA' can be found hidden inside 'major catastrophe'.
(Other definitions for orca that I've seen before include "Killer-whale" , "Cor! a killer whale" , "Large predator" , "ship" , "Predatory black and white toothed whale" .)