Anyone who's seen a Harrison Ford film (7)
I believe the answer is:
witness
'film' 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 don't see?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for witness that I've seen before include "One sees and reports" , "Evidence, proof" , "See (an event or crime)" , "Court testifier" , "Observe - evidence" .)