Commit petty theft (6)
I believe the answer is:
pilfer
'commit petty theft' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pilfer that I've seen before include "Commit minor crime" , "Steal (cheap items)" , "Steal (little things)" , "twenty-two ball game" , "Steal (sl.)" .)