Take legal proceedings against little Susan (3)
I believe the answer is:
sue
I believe this clue is a double definition.
'take legal proceedings against' is the first definition.
'little susan' is the second definition.
(I've seen this before)
(Other definitions for sue that I've seen before include "Apply" , "Take case against in court" , "Take court action" , "Legally challenge" , "- - Barker, 19 star" .)