Volume (4)
(Other definitions for book that I've seen before include "Reserve - bets taken on a race" , "Tome, volume" , "Show yellow card" , "Rebecca or Emma maybe" , "strict regulations" .)
'volume' is the definition.
(a tome is a large or heavy book)
This is the entire clue.
(Other definitions for tome that I've seen before include "Large heavy book" , "Heavy volume" , "Large scholarly volume" , "Large, weighty book" , "Large and scholarly book" .)
'volume' is the definition.
(capacity is a kind of volume)
This is all the clue.
(Other definitions for capacity that I've seen before include "A city cap has ability to contain" , "Potential - role" , "Ability to perform or produce" , "maximum size" , "The amount that something can hold" .)