Czech, say, is so concerned with sound around bathroom (8)
I believe the answer is:
slavonic
'czech say' is the definition.
(czech is a kind of Slavonic)
'sound around bathroom' is the wordplay.
'sound' becomes 'sonic' (sonic means relating to sound).
'around' indicates putting letters inside.
'bathroom' becomes 'lav' (lavatory).
'sonic' enclosing 'lav' is 'SLAVONIC'.
'is so concerned with' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for slavonic that I've seen before include "European" , "Describing some languages" , "Poles" .)