Stress could be grave, for example (6)
I believe the answer is:
accent
I believe this is a double definition.
'stress' is the first definition.
(accent can mean to emphasise or stress)
'be grave for example' is the second definition.
(grave accent is a type of accent mark)
'could' is the link.
(Other definitions for accent that I've seen before include "Distinctive way of talking" , "Tone of voice" , "Emphasis on syllable or local pronunciation" , "A diacritic mark" , "Distinctive manner of oral expression" .)