Across

 1 It helps to keep one on the straight and narrow, even after gin or whisky! (6,5)

10 Hard tunes — yours are numbered (5)

11 Omit Chile when rambling in the style of a sermon (9)

12 Someone doing a good turn may have come from Tasmania, right? (9)

13 Earlier monk (5)

14 Word of prayer around cross before life’s ending with executioners? (6)

16 Somehow that’s living! (8)

18 Biased saint — I do need somehow to get about (3-5)

20 Ass spilling orange (6)

23 Lily’d rewritten rural poem (5)

24 Introduce special price cut (9)

26 English ornament moved a very short distance across the Atlantic (9)

27 A very tiny amount can make one react violently (5)

28 Spirit priest let go free (11)

Down

 2 Character from The Importance of Being Ernest, a solid figure (5)

 3 Book to put aside (7)

 4 Army attacked one island (6)

 5 Cambridge college football team in endless melee playing (8)

 6 Edge between two London districts in darkness (7)

 7 One of two books in which Satan and holiness get written about (13)

 8 Blackening naughty saint that’s taken mixed gin (8)

 9 Red carpet that may come in from the garden (7,6)

15 Each person involved in service — very onerous (8)

17 A degree of illness? (8)

19 Fashionable dance at an uncertain juncture (2,5)

21 Impudence before period when male’s removed item of clothing (7)

22 Worshipper creating a fuss over bishop, full of energy (6)

25 Religious leaders offering one man, a man on Sunday primarily (5)