Party lines a republican originally supports for cash (7)
I believe the answer is:
dollars
'cash' is the definition.
(thesaurus)
'party lines a republican originally supports' is the wordplay.
'party lines' becomes 'doll' (I am not sure about this - if you are sure you should believe this answer much more).
'republican' becomes 'r' (abbreviation).
'originally' suggests taking the first letters.
The initial letter of 'supports' is 's'.
'doll'+'a'+'r'+'s'='DOLLARS'
'for' is the link.
(Other definitions for dollars that I've seen before include "US money" , "US currency" , "American currency" , "Bucks" , "Greenbacks" .)