[rab] By orthography I take it you are referring to the capitalization, in which case, yep, that is the main clue - and is pretty much an accepted method of cluing - as is using punctuation in non-standard ways. The wording of the clue of course refers to the thing that the axeman's victim's head rests upon.
Arkansas ? What's wrong with that - that's where Little Rock is.

[Blob] Well... the executioner is probably a matter of taste - I take the view that you notionally downcase and depunctuate the clue so that what's left tells you what to do. Others disagree, suggesting that if you use 'Bath' in the middle of a clue, it would have to refer to the city as opposed to 'bath' which is a tub. The only way to properly introduce ambiguity is to use it at the start of a sentence. But I'm not that extreme.

On the other hand the Arkansas clue breaks at least two rules. Firstly the definition is not "Little Rock, Arkansas grew up" but simply "Little Rock grew up". And then, if we're being pedantic (which we are), it really ought to be "Little Rock grown up". The second rule is that the definition should never come in the middle of the clue, always at the start or the end.

Everyone has their own stance on what is acceptable and what is not. I consider myself a moderate compared to Ximineans like Don Manley (whose Crossword Manual is well worth a read). However, you might consider me onerously fascist for these opinions.

I entirely agree that the definition must be either at the beginning or the end, not in the middle - but I was referring to the place Boulder, in Colorado ... so "in Colorado" is at the end as required. The Little Rock growing up was the cryptic clue, and the Arkansas for completeness, suggesting a place to be looked for. Even if you objected to this inclusion, spurious words are allowed if they do not fundamentally change the meaning, and I don't think it does.

[rab]I presume you now get the "capital" part of No.5 - as in death (literally head removal).

I think we'll have to agree to disagree about "spurious" words which I believe have no place in a crossword clue. This extends even to articles - the distinction between 'a', 'the' and an unmarked word can be huge in a crossword clue. But this is not really relevant to my beef that "Born in Little Rock, Arkansas - grew up" is not a suitable definition (even a cryptic, subsidiary definition) of "boulder". I accept it's cute that there's a place in the US called Little Rock, and a big rock is a Boulder, which is also a place in the US. I reckon one might be able to make a satisfactory clue out of it. Sadly, I don't think this one is it.

I expect now for you to reveal that it was taken from a Times puzzle...