### Clue: Partner backed up Excel files on this? (6)
### Answer: LAPTOP 
 ### Explanation: Definition: files on this
 **Reversal of**(… backed up, in a down clue) PAL(one's mate/partner) + TOP(to excel/to be better than).
Defn: …, electronic files, that is, including Excel spreadsheets.
… after all, it is a laptop.