Rescue coat tailored a long time ago? (10)

I believe the answer is:

cretaceous

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'a long time ago?' is the definition.
I can't judge whether this definition defines the answer.

'rescue coat tailored' is the wordplay.
'tailored' indicates an anagram (the letters are customised ).
'rescue'+'coat'='rescuecoat'
'rescuecoat' anagrammed gives 'CRETACEOUS'.

Can you help me to learn more?

(Other definitions for cretaceous that I've seen before include "of chalk" , "Chalky" .)

I've seen this clue in The Irish Times.

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