Volume is to include nobleman (8)
I believe the answer is:
viscount
'nobleman' is the definition.
(viscount is a kind of nobleman)
'volume is to include' is the wordplay.
'volume' becomes 'v'.
'to include' becomes 'count' (counting is a kind of including).
'v'+'is'+'count'='VISCOUNT'
(Other definitions for viscount that I've seen before include "plane" , "British noble" , "Minor peer" , "Lord" , "Nobleman" .)