A coin is liquid capital (7)
I believe the answer is:
nicosia
'capital' is the definition.
(capital of Cyprus)
'a coin is liquid' is the wordplay.
'liquid' indicates an anagram.
'a'+'coin'+'is'='acoinis'
'acoinis' with letters rearranged gives 'NICOSIA'.
(Other definitions for nicosia that I've seen before include "Divided city of Cyprus" , "Divided Cypriot capital" , "Largest city on Cyprus" , "It's capital in Cyprus (7)" , "Casino I used in Cyprus" .)