Company incorporating socialist principles (5)
I believe the answer is:
credo
'principles' is the definition.
(I've seen this before)
'company incorporating socialist' is the wordplay.
'company' becomes 'co' (abbreviation).
'incorporating' indicates putting letters inside.
'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 "Words to live by; belief" , "conviction" , "music in church" , "Guiding principles" , "Statement of faith" .)