I have a stinker of a cryptic crossword to finish and am useless at these. Any help would be greatly appreciated.
10ac military men watch part of lines from the centre (6) _ A _ I_ _
20 dn he's been accepted, by letter (6) _ E _ S _ E
21 ac. a fine riddle musical girl is rejecting (4-5) _ _ _ _ _ _ E _ E
24ac Form of lighting in old city's cell (6) - no letters available
26 ac putting something slippery in the pen could be hard (6) - no letters available
22 dn provides support but no barking (5) no letters available but first letter will be first letter of 21ac second word
16dn one hundred sign the letters, impressive results (8) _ T _ _ _ _ _ _ (fourth letter is first letter of 21ac first word and 6th letter will be first letter of 24ac, 8th letter will be first letter of 26ac.