Distinctive badge seen on outside of Danube carriage (8)
I believe the answer is:
delivery
'distinctive badge' 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 don't see?
'seen on outside of danube carriage' is the wordplay.
'seen on' means one lot of letters go next to another.
'outside of' suggests removing the centre.
'carriage' becomes 'livery' (I can't explain this - if you can you should believe this answer much more).
'danube' with its middle removed is 'de'.
'de' put next to 'livery' is 'DELIVERY'.
Can you help me to learn more?
(Other definitions for delivery that I've seen before include "Chinaman, perhaps" , "Consignment" , "Style of speaking" , "useful service for the housebound" , "articulation" .)