Huge soldier has a book (5)
I believe the answer is:
giant
'huge' is the definition.
(I've seen this before)
'soldier has a book' is the wordplay.
'soldier' becomes 'GI' (GI can mean a US soldier).
'has' says to put letters next to each other.
'book' becomes 'nt' (New Testament).
'gi'+'a'+'nt'='GIANT'
(Other definitions for giant that I've seen before include "Monster" , "Creature described in 14 17" , "James Dean film (big one!)" , "Huge; James Dean film" , "Extremely large (person)" .)