Reference work the man has in house (9)
I believe the answer is:
thesaurus
'reference work' is the definition.
(thesaurus is a kind of reference work)
'the man has in house' is the wordplay.
'the man has' becomes 'hes' (contraction of 'he has', meaning 'the man has').
'in' is an insertion indicator.
'house' becomes 'taurus' (Taurus is an example).
'hes' put into 'taurus' is 'THESAURUS'.
(Other definitions for thesaurus that I've seen before include "Book listing synonyms" , "Reference work" , "Word book" , "Wordy gathering" , "Wordy book" .)