Criminals admitting defeat? They may be in the soup (8)
I believe the answer is:
croutons
'they may be in the soup' is the definition.
(croutons may be added to a soup)
'criminals admitting defeat?' is the wordplay.
'criminals' becomes 'cons' (short for convicts).
'admitting' indicates putting letters inside (admit can mean to welcome in or accept).
'defeat?' becomes 'rout' (rout is a kind of defeat).
'cons' enclosing 'rout' is 'CROUTONS'.
(Other definitions for croutons that I've seen before include "Small pieces of toasted bread served in soup" , "Contours in small pieces of toasted bread" , "Contours of bread pieces served with soup" , "Bread bits in soup" .)