Criminal left inside country club — terrible (8)
I believe the answer is:
unlawful
'criminal' is the definition.
(I've seen this before)
'left inside country club terrible' is the wordplay.
'left' becomes 'l' (common abbreviation).
'inside' is an insertion indicator.
'country club' becomes 'UN' (United Nations, group of countries).
'terrible' becomes 'awful' (synonyms).
'un'+'awful'='unawful'
'l' placed into 'unawful' is 'UNLAWFUL'.
(Other definitions for unlawful that I've seen before include "Prohibited by legislation" , "not right" , "Illegitimate" , "Not permitted by the state, contrary to statutes" , "Illicit" .)