Friend set up better mobile device (6)
I believe the answer is:
laptop
'mobile device' is the definition.
'laptop' can be an answer for 'device' (laptop is a kind of device). I'm not sure about the 'mobile' bit.
'friend set up better' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'set up' says the letters should be written in reverse (in a down clue, letters go up).
'better' becomes 'top' (top can mean to better or outdo).
'pal' backwards is 'lap'.
'lap'+'top'='LAPTOP'
Can you help me to learn more?
(Other definitions for laptop that I've seen before include "Type of computer" , "Portable computer" , "device?" , "Aid for businessman" , "Some work on this" .)