Here we go with the first one! A slightly meaty one, but all very nice clues!

Across

1 & 26 across

Lose an opportunity to mess habit around (4,3,4)
MISS THE BOAT — anagram of TO MESS HABIT

3

One Oscar: 'Greatest embodiment of English animal' (10)
WILDEBEEST — WILDE (Oscar), E (English) inside BEST (greatest)

10

One of three in litter unusually acquiring first place (7)
TRIPLET — anagram of LITTER with P

11

Doing hair toss around trophy case (7)
STYLING — SLING (toss) around TY (case of trophy)

12

Accept ire or savagely respond in kind (11)
RECIPROCATE — anagram of ACCEPT IRE OR

13

Unfinished sharp road surface (3)
TAR — unfinished TARt (sharp)

14

Ticked off burden (5)
CROSS — double def.

15

Redrafted aim of ENT's policy statement (9)
MANIFESTO — anagram of AIM OF ENTS

17

Excitedly found excuse to dump ex being inattentive (9)
UNFOCUSED — anagram of FOUND exCUSE

19

Get to sermonise (and not quietly) (5)
REACH — pREACH (sermonise) without p (quietly)

20

Draw little piggy on the phone (3)
TOW — homophone of TOE (little piggy)

22

Releases new cinema tapes (11)
EMANCIPATES — anagram of CINEMA TAPES

25

Pestered injured husband to stand in for wife (7)
HOUNDED — wOUNDED (injured), w (wife) -> H (husband)

27

Senior lapse blocked by wine (10)
ELDERBERRY — ELDER (senior) with ERR (lapse) inside (blocked) BY

28

Tread softly to elect party leaders (4)
STEP — first letters of Softly To Elect Party

Down

1

Engine space goes up over time (5)
MOTOR — reversal of ROOM (space) with T (time) inside

2

Tune out sorceress interrupting so very loudly (6,3)
SWITCH OFF — WITCH (sorceress) inside (interrupting) SO, FF (very loudly)

4

Opening hours: ten 'til regulars turn up (5)
INTRO — reversal of ORTNI (regular letters in HOURS TEN TIL)

5

Scorned alternative sad indie darling initially (9)
DISDAINED — anagram of SAD INDIE, then D (darling initially)

6

Herb put down complaint for Spooner (3,4)
BAY LEAF — Spoonerism of LAY BEEF

7

Be discriminatory in one way, ignoring at first (5)
EXIST — sEXIST (discriminatory) without first

8

Little kid catches one bug on hot plane (5,4)
TIGER MOTH — TOT (little kid) with I (one) GERM (bug) inside (catches), then H (hot)

9

Southbound direction for ski fields? (6)
SLOPES — S (south), LOPE (bound), S (direction)

14

Reportedly grabbed small tool for pump (5,4)
COURT SHOE — homophone of CAUGHT (grabbed), S (small), HOE (tool)

15

Botch smile and handshake (9)
MISHANDLE — anagram of SMILE HAND

16

Begins a degree in beer (6,3)
STARTS OUT — ARTS (a degree) inside STOUT (beer)

18

Cheese stuffing reached Darwin (7)
CHEDDAR — hidden (stuffing) inside reaCHED DARwin

19

Packaging broadcast for Doechii, for example (6)
RAPPER — homophone of WRAPPER (packaging)

21

Cut, twisted and turned (5)
WOUND — triple def.

23

Stop filming here - inside's more appealing (5)
CUTER — CUT (stop filming), hERe (inside letters)

24

Russian leader's promoted new skipping exercise (3,2)
SIT UP — reversal (promoted) of PUTIn'S (Russian leader's) without (skipping) n (new)