1: Tarnish, with bit of dirt, symbol of Superman's composure (9)
6: Reliable, timeless jet (5)
9: Please get tough about rising average temperature (9)
10: Globe's automobile award (5)
11: Gutter seamstress (5)
12: Mad? O, yes! Mad dog! (7)
13: Craft technique for remodeling aged coupe (9)
15: Mineral springs start to moderate involuntary muscular contraction (5)
16: Courses finish with Decline and Fall (5)
17: Evil colleague, for example, breaking in contrary to law (9)
19: Poles in trouble with character from Greece (7)
21: As in 'Lee goes back to the drawing board' (5)
23: Ensemble originally formed with ocarina, cello, theremin, euphonium, and tabla (5)
24: Disorder outside is undermining the state (9)
25: Lovely to have an hour inside for recess (5)
26: Bluff included in reckless dare in ivy league college (9)