Peg put up, coat finally secured, bringing four-letter word! (9)

I believe the answer is:

tetragram

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'four-letter word' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for tetragram that I've seen before include "familiar to geometricians !" , "Say damn (but not blast)" , "Four-letter word" .)

I've seen this clue in The Guardian.

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