Tie it to a thief (6)
I believe the answer is:
bandit
'a thief' is the definition.
(bandit is a kind of thief)
'tie it' is the wordplay.
'tie' becomes 'band' (banding is a kind of tiing).
'band'+'it'='BANDIT'
'to' acts as a link.
(Other definitions for bandit that I've seen before include "Outlaw, robber" , "Violent outlaw" , "Highwayman" , "Thief" , "Armed brigand" .)