Regularly play-acted — Greek character sent up in school (6)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

{p} L {a} Y {a} C {t} E {d} [regularly] then MU (Greek character) reversed [sent up]. Originally the garden at Athens in which Aristotle taught philosophy but later used more generally for a place of learning although ODE now lists this meaning as archaic.