WTO wasted old Trump ally's cash (8)
I believe the answer is:
twopence
'cash' is the definition.
(twopence is a type of coin)
'wto wasted old trump ally's' is the wordplay.
'wasted' is an anagram indicator.
'old trump ally' becomes 'Pence' (Mike Pence, Donald Trump's vice president).
'wto' with letters rearranged gives 'two'.
'two'+'pence'='TWOPENCE'
(Other definitions for twopence that I've seen before include "Low-value coin" , "Penny plain, - coloured" , "Not much money" , "Fiftieth of a pound" , "bit of history" .)