Clergyman absorbed by home-improvement reference book (9)
I believe the answer is:
directory
'reference book' is the definition.
(directory is a kind of reference book)
'clergyman absorbed by home-improvement' is the wordplay.
'clergyman' becomes 'rector' (rector is a kind of clergyman).
'absorbed by' is an insertion indicator.
'home-improvement' becomes 'diy' (abbreviation for 'do it yourself').
'rector' inserted into 'diy' is 'DIRECTORY'.
(Other definitions for directory that I've seen before include "Reference book" , "Telephone information service" , "Book listing names of inhabitants, users etc" , "Telephone book" , "Catalogue" .)