Beam as delivery arrives on time (7)
I believe the answer is:
transom
'beam' is the definition.
(I've seen this before)
'delivery arrives on time' is the wordplay.
'delivery' becomes 'ransom' (sum delivered to a kidnapper).
'arrives on' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'ransom' put after 't' is 'TRANSOM'.
'as' acts as a link.
(Other definitions for transom that I've seen before include "Cross-member of boat or window" , "Horizontal bar across door for matrons" , "Boat's flat stern - horizontal beam" , "Rectangular fanlight" , "Bar above window or door" .)