Soundly construct beams (4)
I believe the answer is:
rays
'beams' is the definition.
(I've seen this before)
'soundly construct' is the wordplay.
'soundly' shows a homophone (sound like).
'construct' becomes 'raise' (raising is a kind of constructing).
'raise' sounds like 'RAYS'.
(Other definitions for rays that I've seen before include "Fish with wing-shaped fins and long tails" , "Beams of sunlight" , "Narrow beams of light" , "Columns of light or heat" , "shafts" .)