Service area, carnage (8)
I believe the answer is:
massacre
'carnage' is the definition.
(thesaurus)
'service area' is the wordplay.
'service' becomes 'mass' (I've seen this in other clues).
'area' becomes 'acre' (I've seen this before).
'mass'+'acre'='MASSACRE'
(Other definitions for massacre that I've seen before include "Murder (of many persons)" , "Mass murder" , "Widespread killing" , "Inflict a heavy defeat" , "Slaughter in large numbers" .)