Lecture room: initially adjust temperature in there (7)
I believe the answer is:
theatre
'lecture room' is the definition.
(as in a lecture theatre)
'initially adjust temperature in there' is the wordplay.
'initially' indicates taking the first letters.
'in' is an insertion indicator.
The initial letters of 'adjust temperature' is 'at'.
'at' put within 'there' is 'THEATRE'.
(Other definitions for theatre that I've seen before include "Scene of operations or dramatic performances" , "Space for dramatic art and surgery" , "where people go to watch" , "Place for stage works" , "Space for drama" .)