1: Small piece of fish (3)
3: Doris has residence in old West African republic (7)
7: What's left when you burn the tree (3)
9: Silent, cat backs away from it (5)
10: Oscillating crystal perhaps not so rare (9)
11: Our Foreign Minister embraced German, and in his own country (4,5)
12: Origins of giddy exhuberant energy -- stunningly emptyheaded! (5)
13: Siamese toolmakers reportedly in colorful clothing (3-4)
14: Very slow backtracking through formulaic algebra (7)
16: Hates and gets rid of a Mensa entry requirement? (7)
17: Mary gets back to business running building trade (7)
18: Screams Yes! around line 50 (5)
19: Television show genre is like this each time (4,5)
21: One who wanders amidst fantastic text is one who is very outgoing (9)
24: Leaders in public office boosted charity foundations (5)
25: Man, what an avant-garde US artist! (3)
26: 'Beat it, mister!' said con man (7)
27: Take Chair in university (3)