Gave letters of authorisation to (10)
I believe the answer is:
initialled
'gave' is the definition.
The definition and answer can be both to do with communicating as well as being past participle verbs.
Perhaps they are linked in a way I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for initialled that I've seen before include "Indicated approving" , "two or three nominal reductions?" , "Recorded agreement" .)