Amount of money invested in large drinks, ten or more (6,7)
'ten or more' is the definition.
(ten is the first number with double figures)
'amount of money invested in large drinks' is the wordplay.
'amount of money' becomes 'figure' (figure is a kind of amount of money).
'invested in' is an insertion indicator.
'large drinks' becomes 'doubles' (a double is a large alcoholic drink).
'figure' going inside 'doubles' is 'DOUBLE FIGURES'.
(Other definitions for double figures that I've seen before include "start at ten", "characters who look alike".)