Scared of a fellow’s assault (6)
I believe the answer is:
afraid
'scared' is the definition.
(similar in meaning)
'a fellow's assault' is the wordplay.
'fellow' becomes 'F' (abbreviation - of a society etc.).
'assault' becomes 'raid' (I've seen this in other clues).
'a'+'f'+'raid'='AFRAID'
'of' acts as a link.
(Other definitions for afraid that I've seen before include "Frightened" , "feeling scared" , "makes one panicky" , "wind up" , "Filled with fear" .)