Largely original company painting (6)
I believe the answer is:
fresco
'painting' is the definition.
(fresco is a kind of painting)
'largely original company' is the wordplay.
'largely' means to remove the last letter.
'original' becomes 'fresh' ('fresh' can be similar in meaning to 'original').
'company' becomes 'co' (abbreviation).
'fresh' with its final letter taken away is 'fres'.
'fres'+'co'='FRESCO'
(Other definitions for fresco that I've seen before include "Method of painting on walls" , "Painting using watercolours on plaster" , "Mural painted on a wall" , "Painting done in wet plaster" , "Picture painted on wet plaster" .)