14d "Overcome by sleep briefly, stop being most lively" (9) 
S?A???E?T    Looks like it could be SNAPPIEST  (there's a nap and and a partial siesta in there) but that would give 20a "Group of pupils oddly is not mad keen" (6)   as  I?T?P?  for which I can't see an answer,
Any help much appreciated