Occupant has awfully neat book (6)
I believe the answer is:
tenant
'occupant' is the definition.
(I know that tenant is a type of occupant)
'awfully neat book' is the wordplay.
'awfully' is an anagram indicator.
'book' becomes 'NT' (New Testament).
'neat' is an anagram of 'tena'.
'tena'+'nt'='TENANT'
'has' is the link.
(Other definitions for tenant that I've seen before include "holder" , "Person renting property" , "Rent payer" , "One renting property" , "Someone who pays rent" .)