Nine clues have a definition containing an extra letter which must be removed before solving..
1a They're used in failing schools primarily to stop criminal charges (5)
28d Joey O'Brien's wicked time (6) ??G?? joy possibly the defn ??
11a Sled's smooth once you've rubbed this scratch (6 , 2 words) ??E / ?U? possibly out for the 2nd word? SL EEK would be smooth ...? eke out ?