Commotion caused by heads of state talking in riddles (4)
I believe the answer is:
stir
'commotion' is the definition.
(stir is a kind of commotion)
'heads of state talking in riddles' is the wordplay.
'heads of' suggests taking the first letters.
The initial letters of 'state talking in riddles' is 'STIR'.
'caused by' is the link.
(Other definitions for stir that I've seen before include "Whisk or mix" , "Sensation" , "Commotion - prison" , "Detention centre" , "Disturb" .)