Computer kept DOS running (7)
I believe the answer is:
desktop
'computer' is the definition.
(desktop computer is a kind of computer)
'kept dos running' is the wordplay.
'running' indicates anagramming the letters.
'kept'+'dos'='keptdos'
'keptdos' anagrammed gives 'DESKTOP'.
(Other definitions for desktop that I've seen before include "Office work surface" , "Main working area of PC" , "often supports a mass of papers?" , "Location of icons" , "Screen display on PC" .)