1: Fill-in professional almost rewrote the column (5)
2: Regular errors in musical application (5)
3: University boards tailless orange and light brown ape (9)
4: Therefore, finish off this bit of work (3)
9: Updike hero taking time off to see teacher (5)
11: Clean oneself, but in reverse (3)
12: Cronkite, Bradley, and Safer's first network (3)