Battle beyond party, that's clear (8)
I believe the answer is:
consomme
'that's clear' is the definition.
(clear soup)
'battle beyond party' is the wordplay.
'battle' becomes 'somme' (Somme is an example).
'beyond' says to put letters next to each other.
'party' becomes 'con' (abbreviation for Conservative Party).
'somme' put after 'con' is 'CONSOMME'.
(Other definitions for consomme that I've seen before include "starter course" , "Clear soup usually of beef, veal or chicken" , "Scone, mom eaten with soup" , "Clear soup made with concentrated stock" , "Liquid food" .)