Wild, wild Wales in the 50s (7)
I believe the answer is:
lawless
'wild' is the definition.
(I have seen 'Wild wild' mean 'lawless' so perhaps 'wild' could also mean 'lawless')
'wild wales in the 50s' is the wordplay.
'wild' indicates an anagram.
'in the' means one lot of letters goes inside another.
'50s' becomes 'ls' ('L' can be a synonym of '50').
'wales' is an anagram of 'awles'.
'awles' inserted within 'ls' is 'LAWLESS'.
(Other definitions for lawless that I've seen before include "Anarchic, without any controls" , "Slew Sal for being criminal" , "disobedient" , "Ungoverned" , "Unruly - anarchic" .)