Risk assessor’s deed unknown by Egypt once (7)
I believe the answer is:
'risk assessor's' is the definition.
(someone calculating insurance risks)
'deed unknown by egypt once' is the wordplay.
'deed' becomes 'act' (I've seen this in another clue).
'unknown' becomes 'y' (algebra).
'by' is a charade indicator (letters next to each other).
'egypt once' becomes 'UAR' (Egypt was once known as the United Arab Republic).
'y' put after 'uar' is 'uary'.
(Other definitions for actuary that I've seen before include "Person using statistics to calculate insurance premiums" , "Accounts statistician" , "Statistician who works for insurance company" , "Risk-assessor" , "One assessing risk" .)