Intones differently to produce stress (7)
I believe the answer is:
tension
'stress' is the definition.
(synonyms)
'intones differently' is the wordplay.
'differently' is an anagram indicator.
'intones' anagrammed gives 'TENSION'.
'to produce' is the link.
(Other definitions for tension that I've seen before include "The effect of force exerted in or on something" , "Strained condition" , "Stretched state" , "Stretched, uneasy, condition" , "Uneasiness" .)