USA cred messed up campaign (7)
I believe the answer is:
crusade
'campaign' is the definition.
(I know that crusade is a kind of campaign)
'usa cred messed up' is the wordplay.
'messed up' indicates an anagram.
'usa'+'cred'='usacred'
'usacred' anagrammed gives 'CRUSADE'.
(Other definitions for crusade that I've seen before include "Advertising campaign" , "religious campaign" , "Religious war" , "Used car involved in campaign for a cause" , "Medieval Christian military expedition to capture the Holy Land" .)