Cruisy Monday morning. I wasn't sure how to classify 18D, but other than that some fun clues and nothing particularly controversial!

Across

1

Got by with crazy English coif (4,2)
MADE DO — MAD (crazy) E (English) DO (coif)

4

Increase rhetoric regarding sheepdog? (4,2)
RAMP UP — RAM (sheep) PUP (dog)

10

Diagram shows how wolf got back and caught deer (9)
FLOWCHART — reversal (got back) of WOLF, C (caught) HART (deer)

11

Produce script for waterfront ceremony (5)
WRITE — W (first letter of water) RITE (ceremony)

12

Provide money to broken down constituents (5)
ENDOW — hidden in brokEN DOWn

13

All very well for attractive fish! (5-4)
HUNKY-DORY — HUNKY (attractive) DORY (fish)

14

Sort of salesman's entrance to port (4-2-4)
DOOR-TO-DOOR — DOOR (entrance) TO DOOR (port)

17

Bottom bits are small potatoes (4)
TOES — partial (small) potaTOES

20

Even dried elks stink (4)
REEK — even letters of dRiEd ElKs

21

Stir ref, lie around in manure (10)
FERTILISER — anagram (around) of STIR REF LIE

23

Listens to Al again at the run-through (9)
REHEARSAL — REHEARS (listens to ... again) AL

25

Able to tour Ireland with a pile of stones (5)
CAIRN — CAN (able) around IR (Ireland)

27

Not quite blue and not extremely plain-spoken (5)
BLUNT — BLUe (without last letter) NT (outside letters of not)

28

Got his first bumpy merger to endure (2,7)
GO THROUGH — GOT H (first letter of his) ROUGH (bumpy)

29

Cheerless listener in an arid environment (6)
DREARY — EAR (listener) inside DRY (arid)

30

Allow rep to return with German (6)
PERMIT — reversal (to return) of REP, MIT (with German)

Down

1

Sounded like cow had a sound frame of mind (5)
MOOED — homophone of MOOD (frame of mind)

2

(& 3-down) The witch aided fools who risk their lives (4,4,5)
DICE WITH DEATH — anagram (fools) of THE WITCH AIDED

5

Used almost all roads every time (6)
ALWAYS — ALl (without last letter) WAYS (roads)

6

So no pious types are toxic? (9)
POISONOUS — anagram (types) of SO NO PIOUS

7

Shame about sweetheart's religious fervour (5)
PIETY — PITY (shame) around E (middle letter of sweet)

8

Criminal's bid is about to end (8)
OFFENDER — OFFER (bid) around END

9

Conspicuous project (5,3)
STAND OUT — double def.

15

Hope Sue has no problem with real estate inspection (4,5)
OPEN HOUSE — anagram (problem) of HOPE SUE NO

16

Address a gent inside an equestrian event (8)
DRESSAGE — hidden in adDRESS A GEnt

18

Sounds like walking on snow with a hair tie (8)
SCRUNCHY — double def.

19

Charlie is introduced to simple trumpet parts by a plucker (8)
PLECTRUM — C (charlie) inside hidden (parts) simPLE TRUMpet

22

Horse's pace is able to get better by half (6)
CANTER — CAN (is able to) TER (half of better)

23

Mad queen gets an offer (5)
RABID — R (queen) A BID (an offer)

24

Wood turner gets in a lather and goes right off (5)
LATHE — LATHEr without r (right)

26

Even signs up to take it to people in the Arctic (5)
INUIT — even letters of sIgNs Up, IT