Campaigns running scared, limiting empty undertakings (8)
I believe the answer is:
crusades
'campaigns' is the definition.
(crusading is a kind of campaigning)
'running scared limiting empty undertakings' is the wordplay.
'running' is an anagram indicator.
'limiting' is an insertion indicator.
'empty' says to hollow out the word (remove centre letters).
'undertakings' with its centre taken out is 'us'.
'scared' anagrammed gives 'crades'.
'crades' enclosing 'us' is 'CRUSADES'.
(Other definitions for crusades that I've seen before include "wars" , "Military expeditions by Christians to recapture the Holy Land" .)