Beam over new story (4)
I believe the answer is:
yarn
'story' is the definition.
('yarn' can be a synonym of 'story')
'beam over new' is the wordplay.
'beam' becomes 'ray' ('ray' can be a synonym of 'beam').
'over' says the letters should be written backwards.
'new' becomes 'n'.
'ray' back-to-front is 'yar'.
'yar'+'n'='YARN'
(Other definitions for yarn that I've seen before include "Story, and thread or wool, say" , "Sailor's tale" , "Cord of twisted fibres, wool say" , "Sort of tale" , "which could unravel?" .)