Chambers is by far the best single-volume, portable dictionary available here. It is recommended as the dictionary of choice for people who complete the country's most difficult crosswords, such as the 'Azed' in 'The Observer'. One of its great advantages for crossword-solvers is that it contains masses of Scottish and other dialect words. These are great favourites with crossword-compilers, because they more easily confuse the largely standard-English speakers who do the puzzles! If you can get one for a fiver, as Sft suggests...get it!