Criminal ring riots intermittently (6)
I believe the answer is:
bandit
'criminal' is the definition.
(I know that bandit is a type of stealer)
'ring riots intermittently' is the wordplay.
'ring' becomes 'band' (synonyms).
'intermittently' means one should take alternating letters.
The alternate letters of 'riots' are 'it'.
'band'+'it'='BANDIT'
(Other definitions for bandit that I've seen before include "Highwayman" , "Desperado" , "Member of a gang of robbers" , "Marauder" , "Dan bit the robber badly" .)