Hipster actor redesigned part of theatre (9,3)
I believe the answer is:
orchestra pit
'part of theatre' is the definition.
('orchestra pit' is part of 'theatre')
'hipster actor redesigned' is the wordplay.
'redesigned' indicates an anagram.
'hipster'+'actor'='hipsteractor'
'hipsteractor' is an anagram of 'ORCHESTRA PIT'.
(Other definitions for orchestra pit that I've seen before include "wind down in one" , "space for musicians" , "Sunken area for theatre musicians" , "Part of a theatre" , "where band plays" .)