Alcram,
22a is one letter for the first four words of the clue, and the rest meaning permit (as a verb) - is also a TV quiz programme
26a can split 3, 4, 2: the first four words, another crossword setter (and theme), wearing - meaning an obscure nsme for an old sailor's hat
23d definition is one of (a particular set of) four, two two-letter words for 'attend' then a quarter of 'lectures'
27d: your D is wrong. The definition is a post that a particular 6d held in regard to people of Corinth and related places; the usual letter for 'good' below ('supporting') a three letter word for (related) people