Heated hostility to many (4)
I believe the answer is:
warm
'heated' is the definition.
(thesaurus)
'hostility to many' is the wordplay.
'hostility' becomes 'war' (war is a kind of hostility).
'to many' becomes 'm' (**).
'war'+'m'='WARM'
(Other definitions for warm that I've seen before include "Moderately hot" , "Pleasantly hot" , "Animated" , "Approaching target" , "Tepid" .)