Squanderer, prodigal (11)
I believe the answer is:
spendthrift
I believe this is a double definition.
'squanderer' is the first definition.
(spendthrift is a kind of squanderer)
'prodigal' is the second definition.
(I know that prodigal can be written as spendthrift)
(Other definitions for spendthrift that I've seen before include "Profligate" , "Irresponsible user of money" , "Squanderer" , "Irresponsible spender" , "Extravagantly spending person" .)