Presumed to hold an amount of money (3)
I believe the answer is:
sum
'an amount of money' is the definition.
(I know that amount can be written as sum)
'presumed to hold' is the wordplay.
'to hold' indicates a hidden word (I've seen 'holding' mean this).
'SUM' is hidden within 'presumed'.
(Other definitions for sum that I've seen before include "Amount of money; add" , "See 25" , "Amount of money; total" , "Mathematical problem" , "Amount, of money say" .)