Authorisation for each task (10)
I believe the answer is:
permission
'authorisation' is the definition.
(I know that permission is a type of authorisation)
'each task' is the wordplay.
'each' becomes 'per' ('per' can mean for each).
'task' becomes 'mission' (I've seen this before).
'per'+'mission'='PERMISSION'
'for' is the link.
(Other definitions for permission that I've seen before include "Visa, eg" , "Consent, authorisation" , "Green light" , "Leave" , "Allowance" .)