Brutal, apart from having silver lining (6)
I believe the answer is:
savage
'brutal' is the definition.
(synonyms)
'apart from having silver lining' is the wordplay.
'apart from' becomes 'save' (I've seen this before).
'having silver' becomes 'ag' (I can't justify this - if you can you should believe this answer much more).
'lining' means one lot of letters goes inside another.
'save' going around 'ag' is 'SAVAGE'.
(Other definitions for savage that I've seen before include "Uncivilized" , "Brutally criticise" , "Menacing, uncivilised" , "Wild and menacing" , "Untamed or undomesticated" .)