Third man to arrive sounds competent (4)

I believe the answer is:

abel

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'third man' is the definition.
(biblical third man after Adam and Cain)

I can't explain the remainder of the clue.

(Other definitions for abel that I've seen before include "One of the first children" , "Slain biblical brother" , "Cain's younger brother" , "Bale out with murder victim" , "one killed early" .)

I've seen this clue in The Globe and Mail.

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