Patriarch's untaxed investment about to be raised (5)
I believe the answer is:
isaac
'patriarch's' is the definition.
(biblical patriarch)
'untaxed investment about to be raised' is the wordplay.
'untaxed investment' becomes 'isa' (Individual Savings Account. I am not sure about the 'untaxed' bit.).
'about' becomes 'ca' (circa).
'to be raised' is a reversal indicator (going up in a down clue).
'ca' backwards is 'ac'.
'isa'+'ac'='ISAAC'
Can you help me to learn more?
(Other definitions for isaac that I've seen before include "Sir -- Newton, English scientist" , "- Newton, Eng. physicist and mathematician" , "Singer" , "Hebrew patriarch" , "Son prepared for sacrifice" .)