Company adopting Socialist principles (5)
I believe the answer is:
credo
'principles' is the definition.
(I've seen this before)
'company adopting socialist' is the wordplay.
'company' becomes 'co' (abbreviation).
'adopting' is an insertion indicator (inserted letters are taken on or adopted).
'socialist' becomes 'red' (socialism is often associated with the colour red).
'co' enclosing 'red' is 'CREDO'.
(Other definitions for credo that I've seen before include "Set of principles" , "music in church" , "Guiding principles" , "I believe in Latin" , "Guiding beliefs" .)