Business listing has unnerved hotel workers (6,5)
I believe the answer is:
yellow pages
'business listing' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'unnerved hotel workers' is the wordplay.
'unnerved hotel' becomes 'yellow' (I am not sure about this - if you are sure you should believe this answer much more).
'workers' becomes 'pages' (page is a kind of worker).
'yellow'+'pages'='YELLOW PAGES'
'has' acts as a link.
Can you help me to learn more?
(Other definitions for yellow pages that I've seen before include "Telephone reference book" , "looking for service here?" , "Reference book for business numbers" , "Directory" .)