Head of ambassadorial party making trouble (3)
I believe the answer is:
ado
'trouble' is the definition.
(thesaurus)
'head of ambassadorial party' is the wordplay.
'head of' suggests taking the first letters.
'party' becomes 'do' (do is a kind of party).
The first letter of 'ambassadorial' is 'a'.
'a'+'do'='ADO'
'making' is the link.
(Other definitions for ado that I've seen before include "Shakespeare: 'Much ... About Nothing'(3) ()" , "Flurry" , "excitement" , "flapping" , "Pother" .)