Stress, emphasise (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)
'emphasise' is the second definition.
(synonyms)
(Other definitions for accent that I've seen before include "Mark used to indecate pronunciation" , "Speech pattern" , "Special emphasis" , "eg Acute" , "Distinctive local way of speaking" .)