Regarded as having hard finish (5)
I believe the answer is:
sheen
'finish' is the definition.
(thesaurus)
'regarded as having hard' is the wordplay.
'regarded as' becomes 'seen' (I've seen this in another clue. I am not sure about the 'as' bit.).
'having' means one lot of letters goes inside another.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'seen' placed around 'h' is 'SHEEN'.
Can you help me to learn more?
(Other definitions for sheen that I've seen before include "Radiance" , "splendid clothing" , "actor?" , "Oil slick" , "brilliance" .)