Force summoned, ran amok (8)
I believe the answer is:
rampaged
'ran amok' is the definition.
(I've seen this before)
'force summoned' is the wordplay.
'force' becomes 'ram' (synonyms).
'summoned' becomes 'paged' (paging is a kind of summoning).
'ram'+'paged'='RAMPAGED'
(Other definitions for rampaged that I've seen before include "ran amok" , "Rushed wildly" , "ran riot" , "Went berserk" , "Charged" .)