Here's the trick: clues marked with an asterisk need to be 4-across before entering them.
But relax - 14, 23-across applies.
Across
1 Make no sound (5)
4 Voicing opinion reveals OK Corral itself (9)
8* Too‐hip cat is florid (9)
9 Unknown driver takes pole in tricky manoeuvre (5)
10, 1‐down* Heathen erred all over the place?! (4, 3, 5)
11* Roughly how fast plenty of 27‐down‐ing could make you, at best (5, 1, 4)
14, 23‐across For sure the reader preserves a yellow‐throated hake, initially at Niagara Falls, but not even fair to use tin! (3, 3, 3, 4, 5)
16* Wonder from the pits (3)
17 Top class business backer (1. 1.)
20 What she held back (2)
22* Small leak (3)
23 See 14‐across
25 Police have the right to take it for a spin?! (10)
26* Part of our digital culture?! (4)
28* Did Thomas find Henry hard to satisfy? (4)
29 King Herod to provide the appetisers (9)
30 Add standard condiments to mashed pear: wet or dry? (9)
31* Source of water everywhere: it's ice! (4)
Down
1 See 10‐across
2 The study of a heretic worth the cost of 29‐across, perhaps? (8)
3 On top of Cleveland grout (4)
4 With nod to Bond girl(s), we look fearful (7)
5 Tight end drew flag for holding (7)
6* Time for 17‐across' trailer, perhaps? (2, 6)
7* Think about gravity failing, sir! (6)
12 Game with no first turn (3)
13* Creature could be a real find (4)
15 A silent remnant (3)
16 Could spend packet blaming second language (4)
18* Also known as a stone fruit, inappropriately (10)
19* Like All in the Family?! (8)
21* Chop nut in half (3)
22* Extra gold plating after 25‐across started up! (4)
23 Climber's final rest could not be more fey (3, 4)
24* He lets one put bet in ‐ at our odds… ?! (1, 6)
25* ...Two‐to‐one's the spot for this hound (6)
27* Almost the length of the bath (3)