Or beset by hostility and extreme wickedness (8)
I believe the answer is:
enormity
'extreme wickedness' is the definition.
'enormity' can be an answer for 'wickedness' (enormity is a kind of wickedness). I am not sure about the 'extreme' bit.
'or beset by hostility' is the wordplay.
'beset by' indicates putting letters inside ('beset' could historically mean 'cover').
'hostility' becomes 'enmity' (synonyms).
'or' placed into 'enmity' is 'ENORMITY'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for enormity that I've seen before include "Great wickedness - more tiny (anag)" , "Vastness - great crime" , "major crime" , "horror" , "Shocking act" .)