Thank you Sue!

Avoids occasionally being seen in terribly poor condition (7)

Direct on the right ccvcvcv two of the vowels are the same

This is another partial anagram

proviso ("poor", anagrammed, contains all the even letters in "avoids")

On the money! ===[**CDM**]===

Thanks, Lex!

I left, needing a second after insipid, dismal isle slides (9)

Direct on the right

This one is also also a partial anagram, coupled with an extremely unusual container.

cvcvccvcc

"slides" is the direct, but "slides sideways" would have been more precise (and if I could have credibly worked sideways slides into the clue, I would have been over the moon!)

sid/esli/ps?

Container is in sip1d (sipd), or this could be where the I left.
Second after = s at the end
Dismal = anagram ind. for isle

Nicely done, Sherlock! ===[**CDM**]===

Hope you had a good birthday Cheryl!

Thank you, Demosthenes!

I had a wonderful birthday, Kevin!

Copper exercises long to get the lead out (5)

Direct on the right. No indicators.

Okay, I admit this is a word I haven't heard before. Denis would wish he thought of it first.

Find a two letter abbreviation for exercise (class) and it'll make it much easier to solve.

I had been thinking this word might begin pe but got no further...

Has to be cu-pe-l (to purify precious metals) which I'd never heard of either

A real "Denis"!

That's the one, Rog! ===[**CDM**]===

Thanks Cheryl!

One that tickled our combined fancy:

Act more savagely to confuse (8)

Bewilder

No trace of bewilderment there, Demosthenes! ===[**CDM**]===

Thanks, Rog!

I think I've finally made this one work:

Iron lands on hotel, then horse rolls. His downfall is swift, but only temporary. (8)

Direct on the right: "downfall" is unusually literal.

So far, so impenetrable...

... might have fe + h (iron lands on hotel)...