Those said to steal undies? (8)
I believe the answer is:
knickers
'undies?' is the definition.
(underwear)
'those said to steal' is the wordplay.
I cannot really see how this works, but
'steal' could be 'nick' (nick can informally mean to steal) and 'nick' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for knickers that I've seen before include "bother" , "Underwear - oh dear!" , "Garment (not to be twisted!)" , "Risk neck (anag.)" , "Undergarments for women" .)