Consider bracketing capsized support beam (7)
I believe the answer is:
radiate
'beam' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for radiate that I've seen before include "Shine" , "Emit (rays or waves)" , "Emit rays; diverge" , "Spread outwards" , "Emit (light, heat, etc)" .)