Thanks, all. Let's kill again:

Tram wreck takes out tables (8)

One 'e'

Hint: Wordplay involves North American slang

Matrices = tables - anagram (wreck) of tram + ices (takes out/kills)

All those Mickey Spillane book which I read many years ago coming in handy...

...and welcome back to the thread Helmer!

Ya got it, Lex! I haven't read Spillane, but I've seen 'The Wizard of Oz'. It's a story about a young woman who travels to an unfamiliar place, where she kills a resident. She then teams up with three other locals, and they all go on to kill again.

Is Isle of Man near Unionville? That is, would you mind getting the belt from manxman?

Thank you Helmer: I am sure manxman can help organise a carrier pigeon.

I am wondering whether perhaps you watched an adaptation of the Wizard of Oz by Elmore Leonard or Quentin Tarantino...

On the basis that "the Belt is in the post," the next clue has to be

Death dealer's merriment on island (12)

Definition on the left, 4 vowels of which 2 are the same

ccvvcccvccvc wordplay 1 + 8 + 3

With the hints, guess it ends in "man"...

UW, you de man!

Authors Karin and Kurt might help you get the whole answer...

TYVM!!

S laughter man (Although the "s" eludes me )

Ah - got it. It's the superfluous s on the end of "dealers"

Happy to oblige, and here is the Belt or a facsimile: I have lost track of who may be hoarding it...
===[**CDM**]===

Thanks Lex! I think it's snuck through a wormhole in space to join all the odd socks and Biro tops that mysteriously vanish...

Waterproofing upper surface say (7)

In the previous crypt, we have "on island" =MAN. Is that 'man' as in 'to occupy'?

(I'd really wanted to make PATHOLOGISTS work. I kinda died trying.)

Think Lex was slipping in a sneaky reference to his homeland, Helmer. Dictionary.com: "Man" - Isle of, an island of the British Isles, in the Irish Sea. 227 sq. mi. (588 sq. km). Capital: Douglas.

Hints for mine:
Direct on the left, one indicator, cvvcvcc

O-kay...
Expanding the clue a smidgen:

Waterproofing room's upper surface say (7)

sealing (sounds like ceiling)

Nice one, Cheryl!

I've polished this up so it's almost indistinguishable from the original... ===[**CDM**]===

Thank you, Rog! Looks very nice.

Roman in chariot, holding back waters (6)

Hope I'm not steppin' on toes: CAESAR

C/aes/AR {chariot=car, waters=sea}

No need to tiptoe here, Helmer: anyone is welcome to jump in any time!

Hail to thee, Helmer! This should help keep your toga in place. ===[**CDM**]===

Thanks, Sherlock. Brings a tear to me eye.

The awkward tear shows concern? (7)

Hints: 2 'e', 1 'a'

? = pun indicator

I was wondering about theatre/theater - the + anagram (awkward) of tear, but could not link that to concern or shows concern as a definition, and now you are talking about a pun I am even more confused...