Academic certificate -- it's upsetting, and Charlie's tactful (10)
I believe the answer is:
diplomatic
'tactful' is the definition.
(similar in meaning)
'academic certificate it's upsetting and charlie's' is the wordplay.
'academic certificate' becomes 'diploma' (I've seen this before).
'upsetting' says the letters should be written in reverse.
'and' is a charade indicator (letters next to each other).
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'it' reversed gives 'ti'.
'diploma'+'ti'+'c'='DIPLOMATIC'
(Other definitions for diplomatic that I've seen before include "Discreet" , "Tactful" .)