Chaos starts to have a very occasional catastrophe (5)

I believe the answer is:

havoc

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'chaos' is the definition.
(I've seen this in another clue)

'starts to have a very occasional catastrophe' is the wordplay.
'starts to' says to take the initial letters.
'very occasional catastrophe' becomes 'voc' (this could be a standard abbreviation I've not previously seen).
The first letter of 'have' is 'h'.
'h'+'a'+'voc'='HAVOC'

Can you help me to learn more?

(Other definitions for havoc that I've seen before include "Chaotic devastation" , "Great confusion" , "Mayhem" , "Chaos and destruction" , "Carnage" .)

I've seen this clue in The Daily Express.

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