I take your point, drxx, but to choose the 'extra letter in definition' gimmick for every clue, where each extra letter is fixed and there are answers as short as one or two letters, is surely what Sir Humphrey Appleby would have called 'a courageous decision'.
I don't generally like the gimmick, but if the setter wanted to stick with the message idea, then 'wordplay delivers an extra letter' would have lent itself perfectly to the purpose. The 'interesting' clue at h1, for instance, could have become 'Drug the Badger (1)', and a4, 'Short book the czar suppresses (2)'.