Also chat about ambassador being a pain (9)
I believe the answer is:
toothache
'a pain' is the definition.
(toothache is a kind of pain)
'also chat about ambassador' is the wordplay.
'also' becomes 'too' (synonyms).
'about' indicates anagramming the letters.
'ambassador' becomes 'HE' (His or Her Excellency).
'chat' is an anagram of 'thac'.
'too'+'thac'+'he'='TOOTHACHE'
'being' is the link.
(Other definitions for toothache that I've seen before include "Odontalgia" , "Oral discomfort" , "Dental problem" , "Pain in the mouth" , "It causes grief" .)