Ring gong in cleaner, sound lab (4,7)
I believe the answer is:
echo chamber
'sound lab' is the definition.
'ring gong in cleaner' is the wordplay.
'ring' becomes 'echo' ('echo' can be a synonym of 'ring'**).
'gong' becomes 'mbe' (Member of the Order of the British Empire).
'in' means one lot of letters goes inside another.
'cleaner' becomes 'char' (charwoman is a type of cleaner).
'mbe' placed into 'char' is 'chamber'.
'echo'+'chamber'='ECHO CHAMBER'
(Other definitions for echo chamber that I've seen before include "part of recording studio?" , "The Cavern might have provided?" , "Alternative to 7 [REVERB]" , "Sound modifier" , "Space that reflects sound" .)