Clear vs. Clearly

I am confuse which one is correct? Both the words sounds natural in the given sentence.

Try to speak as ____ as you can. [Clear, Clearly]

Referring to Oxford

Clear means Easy to perceive, understand, or interpret

and

Clearly means In a clear manner; with clarity.

Both the words fits in the given blank. Which one is correct?

Solution 1:

'Clearly' is the word you need. It describes how you are advised to speak. 'Speak' is a verb, so you need an adverb to modify it. 'Clearly' is an adverb. ['Clear' is an adjective and is used to qualify a noun – but that's not what you're trying to do here.]

Having just given you the official grammatical story, I have to admit that adverbs are gradually going out of fashion, in the UK at least. There is a tendency to use the related adjective instead. But "Try to speak as clear as you can." still sounds wrong to me.

[One adverb that is almost never used these days is "regularly". People say "on a regular basis" instead. Similarly "on a daily basis" is used instead of just "daily". These strike me as weird circumlocutions; they always amuse me.]