[rab] Re-archer: I assume the idea is that it is a double definition. With a dash (hyphen), it can be read as bulls-hitting, which is what archers do. Without, it is what Jeff does. And I've seen "clueless" done that way before, more or less.

[CdM] Thanks - I've got so used to reading 'without' as the opposite of 'within' I forget it can also mean the opposite of 'with'. Also I should have realised this: Cyclops has clued this word in this kind of way before.

I think that clue would be improved by being simply Archer's thing. Like the bust down reason example, it makes the entire clue simultaneously the definition and the cryptic indication.

Well, since BULLS-HITTING isn't a common phrase as far as I'm aware (unlike BULLSHITTING) you'd probably need to write it as Archer's thing? with a question mark.

[CdM] How about OBSCURE VAULT NINETY-NINE?

Yup. :-)

but a better clue might have been:
Hereby ruin sonnet? I'ven't a clue, sorry. (7, 5, 6-4)

Shouldn't be hard... Take on muse, upset as before (6)

[Darren] ASSUME.

There appear to be seven currently outstanding:

• An end to land-mines ! Her idea caused split (8) (Blob)
• This clue might be: "500. Follows solid containing volume of mute's heart" (10) (rab)
• Poster confused near narrow road (6) (Chalky)
• Doctor's wrapped up in umbilical cord (MF)
• Small animal run over by learner driver (6) (rab)
• Twisted small mammal eats a chopped nut (6) (Raak)
• Presume the leader is back in place (8) (Blob)

Perhaps some further hints would be in order. Mine contains a misdirection: "Twisted" is the definition part, not a sign of an anagram.