One clue and a specific time slot sounds like a reasonable compromise to me. To paraphrase nobody in particular, 'it's the taking part that counts'.
Personally, I usually decide on a word at the last minute, but even if the setter has days extra, I think we've all at one time entered what we thought was the sure-fire winner only to find it more or less ignored by the voters.
Speaking of which, I assume that the setter would also be entitled to vote?