Anything a thug has broken (5)
I believe the answer is:
aught
'anything' is the definition.
('aught' means anything)
'a thug has broken' is the wordplay.
'has broken' is an anagram indicator (I've seen this in other clues).
'thug' is an anagram of 'ught'.
'a'+'ught'='AUGHT'
(Other definitions for aught that I've seen before include "Anything (Shakespearean)" , "Nothing" , "Anything at all (archaic)" , "Emphatically anything" .)