Frenchman on flood defence in old capital (4)
I believe the answer is:
mark
'old capital' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'frenchman on flood defence' is the wordplay.
'frenchman' becomes 'm' (abbreviation for Monsieur - like 'Mr').
'on flood defence' becomes 'ark' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'm'+'ark'='MARK'
'in' is the link.
Can you help me to learn more?
(Other definitions for mark that I've seen before include "Former German currency" , "Trace" , "symbol" , "religious work of a saint" , "Characteristic" .)