Cast's regularly seen in that place (7)
I believe the answer is:
theatre
'that place' is the definition.
(I have seen 'Place of entertainment ' mean 'theatre' so perhaps 'place' could also mean 'theatre')
'cast's regularly seen in' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'seen' becomes 'there' (I can't explain this - if you can you should believe this answer much more).
'in' is an insertion indicator.
The alternate letters of 'casts' are 'at'.
'at' put within 'there' is 'THEATRE'.
Can you help me to learn more?
(Other definitions for theatre that I've seen before include "Building for dramas" , "House" , "Globe, say" , "where Finney played" , "Where you might find ham" .)