New threat involving English playhouse (7)
I believe the answer is:
Here is my best explanation:
'playhouse' is the definition.
'new threat involving english' is the wordplay.
'new' indicates anagramming the letters.
'involving' is an insertion indicator.
'english' becomes 'e' (abbreviation).
'threat' is an anagram of 'thatre'.
'thatre' going around 'e' is 'THEATRE'.
(Other definitions for theatre that I've seen before include "stage productions", "hospital room", "natural land formation?", "Show", "Part of hospital", "Scene of action", "Building for the dramatic arts", "Location for plays and operations", "Place for actors" and "Operations room".)