Young boy in Belgium on cutting edge (5)
I believe the answer is:
blade
'cutting edge' is the definition.
(I've seen this in another clue)
'young boy in belgium' is the wordplay.
'young boy' becomes 'lad' (lad can mean a boy or young man).
'in' is an insertion indicator.
'belgium' becomes 'be' (abbreviation as in the top-level domain .be).
'lad' inserted within 'be' is 'BLADE'.
'on' is the link.
(Other definitions for blade that I've seen before include "Leaf, of grass, say" , "Runner on an ice-skate" , "London rail terminus" , "Cutting part of grass?" , "A knife, or a dashing fellow" .)