Freedom of action (5,7)
(Other definitions for carte blanche that I've seen before include "free rein" , "Unrestricted authority" , "Free hand" , "Complete freedom of action" , "Complete authority" .)
'freedom of action' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for autonomy that I've seen before include "'Independence, self-sufficiency (8)'" , "Self-rule" , "form of self-control" , "Self-determination" , "Independence, freedom to govern" .)