Marge - 28 ac is Mersey (the language erse in my, i.e. the setter's)
23d is Gaels, gamelaws with stomach (maw)
29ac Shelta, apparently a language used by vagrants
12 ac is Lymphad, lymph is pure water, puff of course another word for advert and the whole word means Highland galley (my dictionary works overtime on the Saga crossword!)
My thanks to you for your original question mentioning that 18ac began with A, that led me to that solution and to the remaining words, first time I've ever finished this so early but what am I going to do for the next three weeks, which I usually spend mulling over the clues??