It can hardly be in liquid currency! (4,3)
I believe the answer is:
lump sum
'it can hardly be in liquid currency' is the definition.
The definition suggests a singular noun which matches the answer.
This is the entire clue.
Can you help me to learn more?
(Other definitions for lump sum that I've seen before include "Single amount of money" , "as pension may be part-paid?" , "Single payment as opposed to many instalments" , "Amount of money paid all at once" , "Complete payment consisting of a single amount" .)