Where the merry men gathered for a letter? (5,5)

I believe the answer is:

round robin

'a letter?' is the definition.
(round robin is a kind of letter)

I cannot understand how the rest of the clue works.

(Other definitions for round robin that I've seen before include "Circular letter, petition" , "Where mourning birds gathered" , "part of Christmas for some" , "Request presented, with no clear leader" , "Statement signed" .)

I've seen this clue in The Guardian.

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