Issue: point overturned (4)
I believe the answer is:
emit
'issue' is the definition.
(both can mean to give out or radiate)
'point overturned' is the wordplay.
'point' becomes 'e' (E is an example).
'overturned' becomes 'mit' (I can't justify this - if you can you should believe this answer much more).
'e'+'mit'='EMIT'
Can you help me to learn more?
(Other definitions for emit that I've seen before include "Send forth" , "Give off, gas say" , "Let out" , "Exude" , "Give out or put forth" .)