Drank with heads of state when permitted (9)
I believe the answer is:
swallowed
'drank' is the definition.
'heads of state when permitted' is the wordplay.
'heads of' indicates taking the first letters.
'permitted' becomes 'allowed' ('allow' can be a synonym of 'permit').
The initial letters of 'state when' is 'sw'.
'sw'+'allowed'='SWALLOWED'
'with' is the link.
(Other definitions for swallowed that I've seen before include "Meekly accepted" , "Gulped" , "Ingested" , "drunk maybe" , "believed" .)