[Pervinca Took]

BELERIAND: Venture untruth and note well: be troubled, for here be webs of horror!

The straight part of the clue is at the end, and comes from the fact that there were webs of giant spiders in the land of BELERIAND. Frodo uses these exact three words (just prefaced by the past tense) to Sam when they are trapped in Shelob's Lair and the Lady's Phial shows that it is thick spiders' webs that are in their way:

'Come! Let us see what Sting can do. It is an elven-blade. There were webs of horror in Beleriand where it was forged. But you must be the guard and hold back the eyes. Take the star-glass and do not be afraid. Hold it up! Watch!'

So from the first part of the clue, we need to collect the right letters to end up with BELERIAND.

To 'venture' is to DARE.
An 'untruth' is a LIE.
The Latin for 'note well' is 'nota bene,' which is commonly abbreviated as NB and used in taking notes to flag up something that is very important to remember.

DARE + LIE + NB - and 'be troubled' is the anagram indicator, which means you have to trouble/mix/scramble those letters to end up with the answer. (Other words that indicate an anagram are spin/confuse(d)/muddle(d), etc.)

EDIT - I didn't know this would start a new page, so just to say that Nerwen was correct and it is now her go! (As posted on the last page).