Heavy coffins destabilised a cargo ship (10)

I believe the answer is:

sarcophagi

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'heavy coffins' is the definition.
'sarcophagi' can be an answer for 'coffins' (sarcophagus is a kind of coffin). I'm unsure of the 'heavy' bit.

'destabilised a cargo ship' is the wordplay.
'destabilised' indicates an anagram (the order of letters is destabilised).
'a'+'cargo'+'ship'='acargoship'
'acargoship' anagrammed gives 'SARCOPHAGI'.

Can you help me to learn more?

(Other definitions for sarcophagi that I've seen before include "Stone tombs" , "Ancient caskets" .)

I've seen this clue in The Times.

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