Figure on banknote Washington designate a Republican king (9)
I believe the answer is:
watermark
'figure on banknote' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'washington designate a republican king' is the wordplay.
'washington' becomes 'wa' (abbreviation for the US state).
'designate' becomes 'term' (I've seen this in another clue).
'republican' becomes 'R' (political abbreviation).
'king' becomes 'K' (chess abbreviation).
'wa'+'term'+'a'+'r'+'k'='WATERMARK'
Can you help me to learn more?
(Other definitions for watermark that I've seen before include "Line showing maximum flood level" , "Security device, on paper" , "Design in paper" , "Paper manufacturer's identification" , "faint pattern" .)