This crossword No. 15291 clues and answers were published on Sat 11 May 2019 and the puzzle can be visited by following The Guardian Quick Crossword No. 15291 link.
All Across Clues and Answers:
1-across – Opportunities : CHANCES
8-across – Element sharing an atomic number with another but with different physical properties : ISOTOPE
9-across – Word made up of initial letters : ACRONYM
10-across – Own : POSSESS
11-across – Register : ENROL
13-across – Appalling : ATROCIOUS
15-across – Heart chamber : VENTRICLE
18-across – Disreputable — out of the sun : SHADY
21-across – Ship’s windlass used for lifting heavy weights : CAPSTAN
22-across – Small area off a kitchen : DINETTE
23-across – Vocal vibrato — lot more : TREMOLO
24-across – No longer active : RETIRED
All Down Clues and Answers:
1-down – Fad : CRAZE
2-down – Clothes-drying frame : AIRER
3-down – Big blaze : CONFLAGRATION
4-down – Silly smile : SIMPER
5-down – Conker tree : HORSECHESTNUT
6-down – Regain consciousness : COMETO
7-down – Camera attachments : LENSES
12-down – Designation — reputation : NAME
14-down – Second-hand : USED
15-down – Leave : VACATE
16-down – Sibling’s son : NEPHEW
17-down – Large American vulture : CONDOR
19-down – Following : AFTER
20-down – Bring in — give up : YIELD
This crossword has in total 26 where 12 are across and 14 are down.