Across 1. Shellfish, one is told, may substitute for brawn (6) 4. It is allegorical if my cane has lost its tip (6) 9. A right, once more, to turn back to the Falls (7) 10. Credit is given, in total, to the rugby pack (5) 11. The innocent victim is a bird (4) 12. The chamber Othello retired to (4) 13. Further research shows how wrong it will go (3) 15. Support an actor may have in hand (4) 16. Squadron-leader joining the outfit for take-off (4) 19. Lettuce, price of which is reduced (3) 21. Or it may be the centre of the archery target (4) 22. Ring the changes with an expression of delight (4) 24. One Muse was found in a corner at Olympus (5) 25. They spell out the ends for miner, it might appear (7) 26. It is the heart of the nut we are told that sounds higher than major (6) 27. New lag may turn to fix it (6) Down 1. He’s coping with a pen-pusher, this legal employee (8,5) 2. It is a shellfish the edges of which one will cut in curves (7) 3. Impetuosity shown in polite language (4) 5. Such cover-ups in the Muslim world render Sam shaky (8) 6. A number equal to none in terms of company (5) 7. Sort of full cover motorist takes out for school (13) 8. Table bird has its head covered (5) 14. My French greylag is not a bird but a mammal (8) 17. This point, critical in one’s life, may be going off (7) 18. Blood coagulates with carbon – masses of it (5) 20. With this case one expects to get a rise (5) 23. Mme Callas didn’t begin with this bit of opera (4)