Example of punctuation almost unprecedented in official statement (10)
I believe the answer is:
communique
'official statement' is the definition.
(as in a military communique)
'example of punctuation almost unprecedented' is the wordplay.
'example of punctuation' becomes 'comma' (comma is a type of punctuation mark).
'almost' means to remove the last letter (most of the word but not all of it).
'unprecedented' becomes 'unique' (something unprecedented is unique).
'comma' with its last letter taken away is 'comm'.
'comm'+'unique'='COMMUNIQUE'
'in' is the link.
(Other definitions for communique that I've seen before include "Official announcement" , "Source of news" , "Official statement" .)