A head of state transmitted approval (6)
I believe the answer is:
assent
'approval' is the definition.
(I've seen this before)
'a head of state transmitted' is the wordplay.
'head of' suggests taking the first letters.
'transmitted' becomes 'sent' ('send' can be a synonym of 'transmit').
The initial letter of 'state' is 's'.
'a'+'s'+'sent'='ASSENT'
(Other definitions for assent that I've seen before include "Accede, acquiesce" , "Agreement or concurrence" , "Okay" , "Permission" , "Give consent" .)