Public school, distress! (6)
I believe the answer is:
harrow
I believe this clue is a double definition.
'public school' is the first definition.
(I've seen this before)
'distress' is the second definition.
(I've seen this before)
(Other definitions for harrow that I've seen before include "Soil-breaking implement" , "Equipment used in ground-breaking" , "A school; agricultural implement" , "English public school - farm implement" , "Till" .)