Terribly grieved, draw apart (7)
I believe the answer is:
diverge
'draw apart' is the definition.
(synonyms)
'terribly grieved' is the wordplay.
'terribly' is an anagram indicator.
'grieved' with letters rearranged gives 'DIVERGE'.
(Other definitions for diverge that I've seen before include "Move away from" , "separate" , "Grieved to go in different directions" , "Turn apart" , "stray from course" .)