Happen to seize young man in vampire movie (5)
I believe the answer is:
blade
'vampire movie' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'happen to seize young man' is the wordplay.
'happen' becomes 'be' (I've seen this in another clue).
'to seize' means one lot of letters goes inside another.
'young man' becomes 'lad' (lad can mean a boy or young man).
'be' going around 'lad' is 'BLADE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for blade that I've seen before include "Leaf, of grass, say" , "London rail terminus" , "See 24 Across" , "Sword" , "Cutting part of grass?" .)