Word used in pricing a period piece
I believe the answer is:
per
'word used' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'pricing a period piece' is the wordplay.
'pricing a period' becomes 'pe' (I can't justify this - if you can you should give a lot more credence to this answer).
'piece' becomes 'r' (abbreviation for Rook).
'pe'+'r'='PER'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for per that I've seen before include "Preposition meaning for each" , "For each or every" , "Preposition indicating by means of" , "According to" .)