Radio set close to subject expert (6)
I believe the answer is:
adroit
'expert' is the definition.
(adroit can mean expert or masterful)
'radio set close to subject' is the wordplay.
'set' indicates an anagram (instruction to set the letters).
'close to' says to take the final letters (the close/ending of).
The final letter of 'subject' is 't'.
'radio' with letters rearranged gives 'adroi'.
'adroi'+'t'='ADROIT'
(Other definitions for adroit that I've seen before include "Quick and deft" , "Dexterous, artful" , "Apt" , "Skilful or ingenious" , "To raid (anag)" .)