Upper case of liquid assets (7)
I believe the answer is:
capital
I believe this clue is a double definition.
'upper case' is the first definition.
(synonyms)
'liquid assets' is the second definition.
(I've seen this before)
'of' is the link.
(Other definitions for capital that I've seen before include "(Person's) wealth" , "Topping" , "Upper-case letter" , "It's jolly good in the great city" , "Most important city" .)