Cool treat from Sabbath on the radio (6)
I believe the answer is:
sundae
'cool treat' is the definition.
(I've seen this in another clue)
'sabbath on the radio' is the wordplay.
'sabbath' becomes 'sunday' (I have seen 'Christian sabbath' mean 'sunday' so perhaps 'sabbath' could also mean 'sunday').
'on the radio' indicates a 'sounds like' (homophone) clue.
'sunday' sounds like 'SUNDAE'.
'from' acts as a link.
(Other definitions for sundae that I've seen before include "Ice cream served with fruit and syrup" , "Ice cream with toppings" , "Sounds like a day for the ice-cream dish" , "Ice cream confection sounding sabbatical" , "Ice-cream dessert" .)