Criminal ring associated with Congress (6)
I believe the answer is:
bandit
'criminal' is the definition.
(I know that bandit is a type of stealer)
'ring associated with congress' is the wordplay.
'ring' becomes 'band' (synonyms).
'associated with' says to put letters next to each other.
'congress' becomes 'it' (congress can mean sex).
'band'+'it'='BANDIT'
(Other definitions for bandit that I've seen before include "Marauder" , "Armed outlaw" , "Highwayman" , "Enemy aircraft" , "Outlaw, robber" .)