Movement of English runner on plain (8)
I believe the answer is:
overture
'movement of english' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'runner on plain' is the wordplay.
'runner' becomes 'ure' (River Ure).
'on' means one lot of letters go next to another.
'plain' becomes 'overt' (both can mean visible or obvious).
'ure' put after 'overt' is 'OVERTURE'.
Can you help me to learn more?
(Other definitions for overture that I've seen before include "Introduction to, eg, an opera" , "musical composition" , "Orchestral music at the beginning of an opera" , "used in attempt to seduce?" , "Orchestral introduction to an opera" .)