Campaigns that could make us scared (8)
I believe the answer is:
crusades
'campaigns' is the definition.
(Crusade is an example)
'could make us scared' is the wordplay.
'could make' indicates an anagram.
'us'+'scared'='usscared'
'usscared' is an anagram of 'CRUSADES'.
'that' is the link.
(Other definitions for crusades that I've seen before include "Military expeditions by Christians to recapture the Holy Land" , "wars" .)