SOLUTION TO PRIZE CROSSWORD No 15,686:

ACROSS: 6 Collective noun. 9 Old age. 10 Anaconda. 11 Username. 13 Impart. 15 Adjust. 17 Encore. 19 Stigma. 20 Notified. 22 Scenario. 24 Narrow. 26 Plain chocolate. DOWN: 1 Ecclesiastical. 2 Flea. 3 Geneva. 4 Aviation. 5 Undo. 7 Travel. 8 Underdeveloped. 12 Rejig. 14 Proof. 16 Shamrock. 18 In toto. 21 Tendon. 23 Nail. 25 Roan.