Almost beat a Republican star (6)
I believe the answer is:
pulsar
'star' is the definition.
(I know that pulsar is a type of neutron star)
'almost beat a republican' is the wordplay.
'almost beat' becomes 'puls' (I can't explain this - if you can you should believe this answer much more).
'republican' becomes 'r' (abbreviation).
'puls'+'a'+'r'='PULSAR'
Can you help me to learn more?
(Other definitions for pulsar that I've seen before include "A source of space of radio signals" , "Rapidly rotating star, emitting electromagnetic waves very quickly" , "Regularly radiating stellar object" , "Star producing radio waves" , "Heavenly emitter of radio waves" .)