Looter overlooking a cavalryman (5)
I believe the answer is:
rider
'cavalryman' is the definition.
(thesaurus)
'looter overlooking a' is the wordplay.
'looter' becomes 'raider' ('raider' can be a synonym of 'looter').
'overlooking' is a deletion indicator.
'raider' with 'a' taken out is 'RIDER'.
(Other definitions for rider that I've seen before include "in the dressing room before the show?" , "knight" , "One in the saddle" , "One backing a horse" , "Extra provision" .)