Shoota I won't disagree with you, but how is it that many who did the crossword managed to fit 'yeast' in unless of course there are no crossers to get in the way of any alternatives.
I didnt realise that 'a straight line' was a description and not part of the clue.
But both Monty and the second example I found have T??SY which precludes Yeast (and Tasty come to that...)
Mybe it's an Irish word?