This crossword No. 9136 clues and answers were published on Fri 13 Aug 1999 and the puzzle can be visited by following The Guardian Quick Crossword No. 9136 link.
All Across Clues and Answers:
1-across – Harmonica : MOUTHORGAN
7-across – Opening : ORIFICE
8-across – Flower – lit up : TULIP
10-across – Support on which ship is built : KEEL
11-across – Stronghold : FASTNESS
13-across – Eraser : RUBBER
15-across – Base : BOTTOM
17-across – Greenhouse : ORANGERY
18-across – Prison – commotion : STIR
21-across – Tally : MATCH
22-across – Large tent : MARQUEE
23-across – Suffering from insomnia? : LYINGAWAKE
All Down Clues and Answers:
1-down – Type of corn : MAIZE
2-down – Single person – group of people : UNIT
3-down – Braying sound of donkey : HEEHAW
4-down – Cycle – revolution : ROTATION
5-down – Illness : AILMENT
6-down – Where gym users get changed : LOCKERROOM
9-down – Autopsy : POSTMORTEM
12-down – Stretch out : LENGTHEN
14-down – Brutal : BEASTLY
16-down – Peninsula, scene of war 1853-56 : CRIMEA
19-down – Cessation of hostilities : TRUCE
20-down – Opera song : ARIA
This crossword has in total 24 where 12 are across and 12 are down.