Workers get on with rook that is in a zoo (9)
I believe the answer is:
menagerie
'a zoo' is the definition.
(a menagerie is a collection of animals)
'workers get on with rook that is' is the wordplay.
'workers' becomes 'men' (men can mean staff or employees).
'get on' becomes 'age' (synonyms).
'with' is a charade indicator (letters next to each other).
'rook' becomes 'R' (chess abbreviation).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'men'+'age'+'r'+'ie'='MENAGERIE'
'in' is the link.
(Other definitions for menagerie that I've seen before include "[TENNESSEE WILLIAMS] work in part" , "Assembly of animals" , "where the occupants behave like animals" , "place to keep animals" , "lots of animals" .)