Understanding feeling of dread (12)
I believe the answer is:
apprehension
I believe this clue is a triple definition!
'understanding' is the first definition.
(I know that understanding can be written as apprehension)
'feeling' is the second definition.
(apprehension is a kind of feeling)
'of' acts as a link.
'dread' is the third definition.
(I know that dread can be written as apprehension)
(Other definitions for apprehension that I've seen before include "Understanding; anxiety" , "Uneasy concern" , "Anxious anticipation; understanding" , "Trepidation" , "Fearful anticipation" .)