Force of speech for the audience (6)
I believe the answer is:
torque
'force' is the definition.
(torque is a kind of force)
'speech for the audience' is the wordplay.
'speech' becomes 'talk' (I've seen this before).
'for the audience' indicates a 'sounds like' (homophone) clue.
'talk' is a homophone of 'TORQUE'.
'of' acts as a link.
(Other definitions for torque that I've seen before include "Turning force" , "Rotational force; necklace" , "Twisting force; metal necklace" , "Force causing rotation in mechanism" , "Necklace of twisted metal" .)