Decorative finish, chief carpenter used at apartment, to cover first radiator (6)
I believe the answer is:
chrome
'decorative finish' is the definition.
'chrome' can be an answer for 'finish' (I have seen 'Brilliant finish' mean 'chrome' so perhaps 'finish' could also mean 'chrome'). I'm not sure about the 'decorative' bit.
'chief carpenter used at apartment to cover first radiator' is the wordplay.
'chief' suggests taking the first letters.
'used at apartment' becomes 'home' (I can't justify this - if you can you should give a lot more credence to this answer).
'to cover' is an insertion indicator.
'first radiator' becomes 'r' (hst letter of 'radiator').
The first letter of 'carpenter' is 'c'.
'home' placed around 'r' is 'hrome'.
'c'+'hrome'='CHROME'
Can you help me to learn more?
(Other definitions for chrome that I've seen before include "Metal plating - type of yellow" , "Shiny metal for plating" , "Shiny metallic plating" , "Shiny metallic coating" , "Plate (for bathroom fixtures etc)" .)