Power of decision (3-2)
I believe the answer is:
say-so
'power of decision' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for say-so that I've seen before include "Authority - rumour" , "Authority to make a decision" , "Mere assertion (colloq.)" , "Authority to make or allow something to happen" , "Authorisation" .)