Steal underwear (4)
I believe the answer is:
slip
I believe this clue is a double definition.
'steal' is the first definition.
(synonyms)
'underwear' is the second definition.
(I know that slip is a type of underwear)
(Other definitions for slip that I've seen before include "Silly little mistake" , "printer's proof" , "Cutting" , "Minor error; garment" , "Underwear" .)