Long time in enclosure being theatrical (6)
I believe the answer is:
stagey
'theatrical' is the definition.
(I've seen this in another clue)
'long time in enclosure' is the wordplay.
'long time' becomes 'age' (an age is a period of time).
'in' means one lot of letters goes inside another.
'enclosure' becomes 'sty' (sty is a kind of enclosure).
'age' placed within 'sty' is 'STAGEY'.
'being' acts as a link.
(Other definitions for stagey that I've seen before include "Much too theatrical" , "Excessively dramatic" , "camp" , "may be exaggerated" .)