Boatman's following silent film, a universal horror (5)
I believe the answer is:
mummy
'film a universal horror' is the definition.
(The Mummy is a Universal Pictures horror film)
'boatman's following silent' is the wordplay.
'boatman's' becomes 'my' (where the crossword setter is 'Boatman').
'following' means one lot of letters go next to another.
'silent' becomes 'mum' (synonyms).
'my' put after 'mum' is 'MUMMY'.
(Other definitions for mummy that I've seen before include "Embalmed corpse" , "Preserved Egyptian" , "Mother (found in ancient Egypt?)" , "Embalmed Egyptian" , "Possible call from child" .)