The usual pleasing fare from Quixote in the final IoS puzzle of the year. I found it fairly easy, solving time, 15 mins.
Notes on some clues below, happy to explain others if asked.
* = anagram
ACROSS
10 S (CO) URGES
11 DENTISTS CHAIR patienT in (scared in this)*
13 FA (N) T ASIA Asia = country collection
16 LI (CH) GATE
18 SHIRLEY TEMPLE US child film star of the 1930s, later diplomat, politician. There’s a Shirley, near Birmingham, England.
21 IBERIS Of which candytuft is an example “maybe” – Iberia’s “lacking a”.
DOWN
19 LIVID (devilish)* less the letters of “he’s”. Unusual but fair – indicated by ‘terribly’