Magazine company must introduce colour at the outset (5)
I believe the answer is:
comic
'magazine' is the definition.
(comic is a kind of magazine)
'company must introduce colour at the outset' is the wordplay.
'company' becomes 'co' (abbreviation).
'at the outset' suggests taking the first letters (the outset is the beginning).
The initial letters of 'must introduce colour' is 'mic'.
'co'+'mic'='COMIC'
(Other definitions for comic that I've seen before include "Droll - comedian" , "Child's magazine" , "Professional funny person" , "Funny man, may be stand-up" , "Funny man, often stand-up" .)