TWO-WAY TEASER

ACROSS: 1 Proof, 4 Tripper, 8 Contradictory, 10 Solve, 11 Duke, 12 List, 16 Upper, 17 Pharmacopoeia, 19 Retired, 20 Domed. DOWN: 1 Pickled pepper, 2 Own, 3 Forest, 4 Toddle, 5 Inches, 6 Promising, 7 Royal standard, 9 Takes part, 13 Summer, 14 Spaced, 15 Tripod, 18 Elm.