1: There aren't any comebacks after such a poor performance. (2, 7)
2: Best work it out with mother (7)
3: Privy to accessibility (11)
4: Freshen the atmosphere (3)
5: Vagrant's foot caught in spinning machine (7)
6: Nothing we have to pay (3)
7: Technique for picking up new material? (5)
10: Be of use to a head covering, we hear (5)
12: Mann's 'Death in Venice' Dorothy sent up (3)
13: Incomplete raw data lies in largely unexplored regions (4,7)
17: At first, Sonny and Cher having bizarre duel with one providing slots? (9)
19: Sexy Liberal goes to small United States Territory (5)
20: Talk about rent for a piece of property (7)
21: Height is equal to three-fifths of the first one (3)
22: Evil twin and its dupes (7)
23: Fur seal frolicking around entrance to bay (5)
26: Vet theatre opening 8-down (3)
27: Get into the archeology scene. (3)