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' says to take the initial letters (I've seen 'pieces of' mean this).
'wood' becomes 'd' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
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" .)