6  Swindle involving grub; little bread cube (7)

 7  Learn about one unspecified deep ravine (6)

 9  Be up against advanced objection (4)

10 Citrus fruit of a pope (a gentle one) (10)

11 Switch positions occasionally (2,3,3)

13 One French trade show marked by deception (6)

15 Shorthand within Middle Eastern letter (4)

17 Soft creamy cheese containing hint of naturally salty water (5)

18 Bitterness of topped golf stroke (4)

19 Gutless doctor rejected conservative disease (3 3)

20 In disarray, drily see those who give in (8)

23 Mechanic's strength getting round problem with resistance (10)

26 Polish unknown gem (4)

27 Adult, open-mouthed stares for feasts to celebrate love (6)

28 Upset involving river, made a slip in accuracy (7)

 2  Building material revolutionary company cuts up (6)

 3  Surprisingly keen to hit somebody with leg joint (4)

 4  Tortuous clue she'd programme (8)

 5  Somewhat malign attacking insect (4)

 6  Taxi inside wooden hut (5)

 8  Piggy noises of boy endlessly daubing with printing fluid (7)

12 Sprite's pretty unknown (5)

14 Expression of disgust, gutless lad stumbles and falls in school outings (5,5)

16 Hospital making a mistake producing seafood (7)

17 Merely lock for support (8)

21 Necessitate turning in late (6)

22 Fanatical artist with attempt to achieve something (5)

24 Not completely spilt, upended, overflows the edges (4)

25 In the auditorium manner of running total entrance money (4)