Liquid asset in a town on the Thames (7)
I believe the answer is:
staines
'a town on the thames' is the definition.
(I've seen this before)
'liquid asset in' is the wordplay.
'liquid' is an anagram indicator.
'asset'+'in'='assetin'
'assetin' with letters rearranged gives 'STAINES'.
(Other definitions for staines that I've seen before include "Town SW of Heathrow" , "Surrey town on Thames" .)