Comes clean, confesses (4,2)
I believe the answer is:
owns up
I believe this clue is a double definition.
'comes clean' is the first definition.
(I've seen this in another clue)
'confesses' is the second definition.
(to own up is to confess)
(Other definitions for owns up that I've seen before include "Allows" , "'Comes clean, confesses (4,2)'" , "Admits responsibility" , "Admits blame" , "Confesses, admits guilt" .)