Insurance professional, sometimes called "a cross between a bookie and an undertaker” (7)
I believe the answer is:
actuary
'insurance' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for actuary that I've seen before include "Professional calculator of insurance statistics" , "One assessing risk" , "Specialist who calculates probabilities for insurance companies" , "Assessor of insurance risks" , "One calculating risk for insurance companies" .)