Computer chum set up, prime requirement for tackling work (6)
I believe the answer is:
lap-top
'computer' is the definition.
(I've seen this before)
'chum set up prime requirement for tackling work' is the wordplay.
'chum' becomes 'pal' ('pal' can be a synonym of 'chum').
'set up' says the letters should be written in reverse.
'prime requirement for' suggests taking the first letters (the first or prime letter required by the word).
'work' becomes 'op' (abbreviation for opus).
The first letter of 'tackling' is 't'.
'pal' backwards is 'lap'.
'lap'+'t'+'op'='LAP-TOP'
(Other definitions for lap-top that I've seen before include "Portable computer, sits on knee" , "Kind of computer" , "Portable computer, used while travelling" , "Type of computer" , "Personal computer" .)