Last Letter to the Corinthians? (5)

I believe the answer is:

omega

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'last letter' is the definition.
(last letter of the Greek alphabet)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for omega that I've seen before include "Greek long 'o'" , "Ultimate letter" , "Final Greek letter" , "character in Greek literature?" , "letter to Greeks" .)

I've seen this clue in The Telegraph.

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