Make further adjustment concerning the radio (5)
I believe the answer is:
reset
'make further adjustment' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'concerning the radio' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'the radio' becomes 'set' (I've seen this in other clues).
're'+'set'='RESET'
Can you help me to learn more?
(Other definitions for reset that I've seen before include "button on electronic device?" , "Restore to the initial readings" , "Restore to zero" , "question that's appeared in exam again" , "do this to make adjustment" .)