Emphasis on Diana in pain (8)
I believe the answer is:
distress
'pain' is the definition.
(I know that distress is a type of pain)
'emphasis on diana' is the wordplay.
'emphasis' becomes 'stress' (synonyms).
'on' is a charade indicator (letters next to each other).
'diana' becomes 'Di' (Di is short for Diana).
'stress' put after 'di' is 'DISTRESS'.
'in' is the link.
(Other definitions for distress that I've seen before include "Extreme anxiety or sorrow" , "Misery" , "Severe pain" , "Unhappiness" , "Affliction" .)