Observe ambassador meeting newspaper boss (4)
I believe the answer is:
heed
'observe' is the definition.
(thesaurus)
'ambassador meeting newspaper boss' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'meeting' means one lot of letters go next to another.
'newspaper boss' becomes 'ed' (I've seen this in other clues).
'he'+'ed'='HEED'
(Other definitions for heed that I've seen before include "Pay close attention to" , "Care, attention (paid)" , "Observe" , "Consider" , "Be mindful of" .)