ACROSS

 1  An official has to stand behind it! Run across it and it goes up on the board. (4,5)

 6  Cause a couple of hands to get together, and go up and down. (5)

 9  One doesn’t like to run it when sailing. (7)

10  Made reference to the fact that everything gets sort of due, with a barely passing grade. (7)

11 , 12 and 13 6 across could get 30, to a point, and earn this title. (3,4,2,4)

15  One of these digs in the sand and lies in wait for the worker going to Long Island briefly, meeting a disturbed offspring. (3,5)

16  In public, ours expect to show where drivers start out at least nine times–and swear about nothing at all! (6)

18  and 26 down Where they feel low-down, even at home? Remainder the lady’s property! (11)

20  They’re hailed more often than Caesar was! (8)

23  See 6 down

24  Also dragged around inside in Spain? (6)

25  Possibly low flying at night, traditionally. (3)

28  One who doesn’t play fair makes a bad teacher. (7)

29  I exist in a rainstorm finally, like the Spanish or Portuguese. (7)

30  Perhaps stick with a fork in reaching for the asparagus, in part–or possibly pears, too! (5)

31  Swingers of a sort make them at times. (They reputedly work only in the sunshine!) (9)

DOWN

 1  Earth-shaking type of courage! (5)

 2  Melodic embellishment in your private nook, when little Mortimer is around. (7)

 3  Bob is at one end of such, used if you like things straight up and down. (5,5)

 4  A golf club, when in the sand, possibly. (Fire back on them!) (8)

 5  The wrong name otherwise–a charming one might do it. (6)

 6 , 17 and 23 across To which carts were pulled by hand, and someone finally said, “This is the place!” (4,4,4,4)

 7  A place in Massachusetts also finished here. (7)

 8  Stop those feelings of rage! Such causes possible harm! (9)

14  The Mikado, for example. (5,5)

15  Tells everyone that the young lady has put on a little weight! (9)

17  See 6

19   A flying one might be associated with the air. (7)

21  A plant of the buttercup family, done to a nice turn. (7)

22  A glorious day to many–and part of our thoughts show it! (6)

26  See 18 across

27  The main part comes up with deserters from the ship. (4)