Silly person taking article away from Belgian port (5)
I believe the answer is:
twerp
'silly person' is the definition.
(I've seen this before)
'article away from belgian port' is the wordplay.
'article' becomes 'an' (indefinite article).
'away from' is a deletion indicator.
'belgian port' becomes 'antwerp' (I've seen this before).
'antwerp' with 'an' taken out is 'TWERP'.
'taking' acts as a link.
(Other definitions for twerp that I've seen before include "Numpty" , "Silly-billy" , "Contemptible type" , "Nincompoop" , "ass" .)