1: Demonstrated the way in which to keep poles apart (5)
3: Leaning back, incorporated ruling (9)
8: Three kernels of copper-yellow grain (3)
9: Martyr fighting segregation (5,6)
11: Next to erector is a witness (9)
13: Abstract art is just one step.(5)
14: Writing material on usury: Papacy held it back (7)
15: Expressed willingness to be away before start of day (7)
17: A brutal arrangement in rows and columns (7)
19: When you work it out, Alfie, we fish (7)
21: Children nicely holding back secret (5)
23: A flare-up is getting off 23-across (9)
25: Just grazed the pasty? (4-7)
26: Drawing, for example, a bit of a cartoon (3)
27: Oscillating crystal perhaps not so rare (9)
28: Youngster giving wounded first aid (5)