From Uppsala, a mighty welcome (6)
I believe the answer is:
salaam
'welcome' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'from uppsala a mighty' is the wordplay.
'from' indicates the answer is hidden within the clue.
'SALAAM' can be found hidden inside 'uppsala a mighty'.
Can you help me to learn more?
(Other definitions for salaam that I've seen before include "Oriental salutation meaning peace" , "Oriental greeting with bow of obeisance" , "Masala (anag) - Arabic greeting" , "Oriental greeting or homage" , "Greetings" .)