Fight to save a battered used car (7)
I believe the answer is:
crusade
'fight' is the definition.
(I know that fight can be written as crusade)
'battered used car' is the wordplay.
'battered' indicates an anagram.
'used'+'car'='usedcar'
'usedcar' with letters rearranged gives 'CRUSADE'.
'to save a' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for crusade that I've seen before include "Vigorous campaign" , "Action by Christians to recapture the Holy Land" , "Advertising campaign" , "Drive" , "Used car involved in campaign for a cause" .)