Aggressive horde that is surrounding Liberal (7)
I believe the answer is:
hostile
'aggressive' is the definition.
(associated in meaning)
'horde that is surrounding liberal' is the wordplay.
'horde' becomes 'host' (synonyms).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'surrounding' is an insertion indicator.
'liberal' becomes 'l' (abbreviation).
'ie' going around 'l' is 'ile'.
'host'+'ile'='HOSTILE'
(Other definitions for hostile that I've seen before include "Belligerent" , "Enemy" , "Antagonistic" , "malevolent" , "The soil strangely is unfriendly" .)