Get in line! Popular attendant changing facility (8,4)
I believe the answer is:
dressing room
'changing facility' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'get in line popular attendant' is the wordplay.
'get in line' becomes 'dress' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'popular' becomes 'in' ('in' can mean trendy).
'attendant' becomes 'groom' (I have seen 'Stable attendant' mean 'groom' so perhaps 'attendant' could also mean 'groom').
'dress'+'in'+'groom'='DRESSING-ROOM'
Can you help me to learn more?
(Other definitions for dressing room that I've seen before include "Place to change or store clothes" , "Changing cubicle" , "Feature of a posh address" , "Where actors change" .)