Come down about twisted beam and cord (7)
I believe the answer is:
lanyard
'cord' is the definition.
(I know that lanyard is a type of cord)
'come down about twisted beam' is the wordplay.
'come down' becomes 'land' (to land is to come down after flying).
'about' is an insertion indicator.
'twisted' is a reversal indicator.
'beam' becomes 'ray' (synonyms).
'ray' reversed gives 'yar'.
'land' placed around 'yar' is 'LANYARD'.
'and' acts as a link.
(Other definitions for lanyard that I've seen before include "Cord with whistle attached" , "Line for extending or fastening ship's rigging" , "Part of rigging" , "Rope on ship's rigging" , "Neck cord holding whistle" .)