Pennsylvania city pursuing absurd new mega zoo (9)
I believe the answer is:
menagerie
'zoo' is the definition.
(a menagerie is a collection of animals)
'pennsylvania city pursuing absurd new mega' is the wordplay.
'pennsylvania city' becomes 'erie' (I've seen this in another clue).
'pursuing' is a charade indicator (letters next to each other).
'absurd' indicates an anagram.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'n'+'mega'='nmega'
'nmega' is an anagram of 'menag'.
'erie' put after 'menag' is 'MENAGERIE'.
(Other definitions for menagerie that I've seen before include "Animal exhibition" , "[TENNESSEE WILLIAMS] work in part" , "Beastly lot" , "Animals go in here" , "Collection of wild animals in cages" .)