2: There aren't any comebacks after such a poor performance. (2, 7)
3: Men hate diffused gas (7)
4: Observed no Knight (5)
5: Schoolchildren made to come back on Saturday make mistakes (4-3)
6: Junk food--its odor? Stinky (7)
7: Expose the French heavy weight (3,2)
8: Is big lady in tatters forever? (9)
9: Prohibit an attorney's organization (3)
12: Certain mollusk back in Hokkaido ports again (9)
13: Ice trails guide down to earth (9)
15: Salt sees entrance taking in everyone (7)
16: Press or key source of metal (4,3)
17: There is a Santa, perhaps (7)
18: Church council regulation sounds like a big gun (5)
20: Get into the archeology scene. (3)