But in time, no great credit? (6)
I believe the answer is:
honour
'no great credit?' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'but in time' is the wordplay.
'but' becomes 'on' (I can't explain this - if you can you should believe this answer much more).
'in' means one lot of letters goes inside another.
'time' becomes 'hour' (unit of time).
'on' inserted within 'hour' is 'HONOUR'.
Can you help me to learn more?
(Other definitions for honour that I've seen before include "Be faithful to; glory" , "Show respect or bestow rewards on" , "Symbol of approval or distinction" , "prestigious award" , "Privilege" .)