failing = f(ine)law = rule

Nice one MxM!

Merci Denis ===[**WCF**]===

Merci aussi.

Preserves degree in trees (7) one "e"

e(mba)lms

A good, spooky one!

...I was working in my lab late one night...and out comes ==={**WCF**]===

That sure is an eerie sight!

Bury together, for a start (5)

Inter (double def) = bury, but also together when used as a prefix (for a start)

You buried that one, Lex! ==={**WCF**}===

Thank you m'lady.

Probably dodgy, but:

Hammers and tongs not quite dancing from the lab (7,4)

http://www.youtube.com/watch?v=0thH3qnHTbI

But can't quite see how the "g" in "tongs"
is made to vanish; if "not quite" is intended
to do so.....hmmm: OH Pandora!

Well, he warned us and it IS Halloweeny, if not legal. How about this instead:

Hammers and stone not quite dancing from the lab (7,4)

or: Monster Mash dancing lessons in classroom? (4,7)
for: math sermons !

Correct of course, and I blame Halloween and Denis for any transgression - he was the one who put it in mind!

Here's an accessory to go with the pumpkin
===[**WCF**]===

Thank you, Lex.

Koala, for one, is also French and English! (6)

Aussie

"also" in French = aussi
English = E
Koala, for one = Aussie (Australian)