Riches gained by breaking the law (6)
I believe the answer is:
wealth
'riches' is the definition.
(synonyms)
'breaking the law' is the wordplay.
'breaking' is an anagram indicator.
'the'+'law'='thelaw'
'thelaw' anagrammed gives 'WEALTH'.
'gained by' is the link.
(Other definitions for wealth that I've seen before include "'Riches, affluence (6)'" , "was common under Cromwell" , "An abundance of valuable possessions or money" , "Riches, worldly goods" , "Abundance of resources" .)