Carrier of a hard piece of wood (3)
I believe the answer is:
hod
'carrier' is the definition.
(I've seen this before)
'hard piece of wood' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'piece' indicates taking the first letters (I've seen 'piece of' mean this).
'wood' becomes 'd' (I can't explain this - if you can you should believe this answer much more).
The first letter of 'of' is 'o'.
'h'+'o'+'d'='HOD'
'of a' is the link.
Can you help me to learn more?
(Other definitions for hod that I've seen before include "Bricklayer uses it for carrying" , "Pole used to carry bricks" , "Carrier for a bricklayer" , "Coal-scuttle" , "Trough on pole for carrying bricks" .)