That man's entering The Bull, where spirits and liquor can be found together (9)
I believe the answer is:
thesaurus
'where spirits and liquor can be found together' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'that man's entering the bull' is the wordplay.
'that man's' becomes 'he's' ('he's' as in 'he is').
'entering' is an insertion indicator.
'the bull' becomes 'taurus' (I've seen this before).
'hes' inserted into 'taurus' is 'THESAURUS'.
Can you help me to learn more?
(Other definitions for thesaurus that I've seen before include "Word book" , "Book listing synonyms" , "Wordy gathering" , "Volume of synonyms" , "Reference work" .)