Ambassador briefly produces certificate (7)
I believe the answer is:
diploma
'certificate' is the definition.
(diploma is a kind of certificate)
'ambassador briefly' is the wordplay.
'ambassador' becomes 'diplomat' (I've seen this before).
'briefly' means to remove the last letter.
'diplomat' with its final letter taken away is 'DIPLOMA'.
'produces' acts as a link.
(Other definitions for diploma that I've seen before include "Course certificate" , "Academic certificate" , "Honorific document" , "What a student seeks" , "official document" .)