Such a corrupt fund that is melting messily away (5)
I believe the answer is:
slush
This clue is a double definition.
'such a corrupt fund' is the first definition.
(as in a slush fund)
'that is melting messily away' is the second definition.
(slush is partly melted snow)
(Other definitions for slush that I've seen before include "emotionalism" , "Partially melted snow" , "that has been frozen" , "sentimentality" , "Melting snow" .)