The Listener 4759 - Uniform Uniform- By Istenem

[Matakari]

Good morning, I’m having a go at the Listener for this week
and am encountering some difficulties for which I would
appreciate help. Thanks in advance!

( Answers clash in one cell, which must be filled with the sum of the two letters’ alphabetic positions (A = 1 etc). Six clues need an extra word removed to enable solving; the words in clue order (10, 5, 8, 6, 7, 6) with the clash number describe two inspirational figures. The initials of these clues’ answers cryptically suggest an achievement. Solvers must highlight 28 cells representing both figures. The Chambers Dictionary (2016) is the primary reference.)

ACROSS:
2 Fairly extensive pioneering, somehow losing height (7) : ?L?????
15 Midsize clairvoyant agency is standard (6) : ?N????
17 Substance skins could hold for a bomber (9) : ??T?????A
23 Look right away from scout (4) : ???E
34 Very much ordinary basset was like this (4) : ???O
43 Lassie wanders eastward from Highlands ( 6 ) : ?E??I?

[klazomaniac]

27 Inswinger (singer anag with win inside) ???

[TheWinner]

28. HINT, anagram using "first two" = rare blood group + not Crosby or Stills.

[upsetter]

1 F(ollowing), the French for the, followed by a medal.
14 retired needs to be removed
27 is a cricketing term

[Matakari]

jUST GOT 28 (d)

[upsetter]

I think that Suzi Dent has mentioned it on Countdown.

[TheWinner]

Perfect clue from upsetter for no. 1. A culinary term for setting fire to brandy on a xmas pudding.

[ProfessorMaisie]

20d is obscure, I think -
C(arbon) plus initial letter of 4th word [inside] a word that means to fill with gas/air.

You have most of 'proceeds' [reversed] already - put the Latin abbrev. for 'this year' inside it.

[ProfessorMaisie]

...looks like you might have gone wrong with 45a, Matakari - 20d ends with 's'.

[ProfessorMaisie]

...and 'fills with gas/air', is more precise (sorry).

[Matakari]

Got 20A!

[Matakari]

I've got all except 14d which I'm studying now!

[Matakari]

The last three to set me free for the end game!
Many thanks in advance! And, yes to NACW, I
figured out the last Listener.

21a Jacket’s no good endings in secure prison (4) : BA?U
14d As retired one, mislead junior court (8) : C?N??N??
30d Jersey XI in France’s third-place award, missing first and second (4) : ?NPE

[upsetter]

4 has a clash

[ProfessorMaisie]

30d (has a surplus word) it's a gift for someone with your particular language skills, Matakari. Obviously, no word is possible with the letters you're giving (maybe check the preamble again?). upsetter could be referring to this answer, I'm not sure.
14d (upsetter gave you the surplus word for this one earlier, and has perhaps missed the 1 with his latest hint for 4?) 3 letter word for 'mislead'/cheat + abbreviations of the next two words (3+2).
21 two 3 letter synonyms for 'secure' + 'prison'/receptacle [and remove 'g(ood)' from both].

[hankir]

14d: Junior is Jun.
30d. If first place is Gold, then third place is .....
Jersey is extra word.