These so called 'advanced' crosswords are generally in the barred-grid format as opposed to the standard blocked grid.
With extra checking letters this allows the setter greater scope for including more unusual or obscure words. The setters however see themselves as having a responsibility to offer a level of precision to their clues which generally exceeds those in the blocked-grid crossword.
As a general rule the more obscure the word the more straightforward the clue.
Thank you, K. I undestand what you mean. I'm not very much used to the barred-type yet. Last week's Azed took me days to complete. If this carries on, I won't have time for anything else. And don't tell me, you finished Azed with your cornflakes!