As my first appeal seems to have fallen on stony ground,here the others I can make no progress on (the letters given are pretty certain,I think):
1a Sit-in-the-mud trimmed sailor's horse:???R?B
13a Make face at horse before tack becomes headless: ?U?N
27a Horse's behind replacing tail with love: L?S?N? ---- losing?why?
2d Test uninitiated mountain: ??A? ---oral/ural?
8d Announced game on a horse:B?U?O?N?I?
Surely I can't be the only one stuck here???