Joint delivery of speech (12)
I believe the answer is:
articulation
This clue is a triple definition!
'joint' is the first definition.
(I know that joint can be written as articulation)
'delivery' is the second definition.
(I've seen this before)
'of' is a link.
'speech' is the third definition.
(thesaurus)
(Other definitions for articulation that I've seen before include "clear diction" , "Clarity in speech" , "delivery" .)