It enables the performer to give a double act (6)
I believe the answer is:
encore
This clue could be a double definition.
'it enables the performer' is the first definition.
The definition suggests a singular noun which matches the answer.
'a double act' is the second definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'to give' acts as a link.
Can you help me to learn more?
(Other definitions for encore that I've seen before include "Request for repeat performance" , "(Call for) repeat performance" , "Cry from the audience for more" , "Call for additional item" , "Call to perform again" .)