Aimed to thrash agencies (5)
'agencies' is the definition.
(I've seen this before)
'aimed to thrash' is the wordplay.
'aimed' anagrams to 'MEDIA'.
But, I'm not sure how this is indicated.
Can you help me to learn more?
(Other definitions for media that I've seen before include "Collective name for newspapers, broadcasting etc", "TV networks and the like", "News channels", "Eg, newspapers, TV", "Agencies".)