FRED
Every time you see those adverts where some drooling, technology-addled fool is tapping the icons on the screen of an i-phone, each of these icons represent a particular function of the device. These functions are called "applications" (i.e. tasks to which the electronic wizardry of the device can be applied. The word "application" has now been abbreviated (of course) to "app", as in "How many apps have you got on your Blackberry?" This is the first time I've come across the use of "app" used in this way in a crossword. Chambers gives "apparent(ly, appendix, applied, apprentice, approved, approximate."