Expert in origin of transistor radio's development (6)
I believe the answer is:
adroit
'expert' is the definition.
(adroit can mean expert or masterful)
'origin of transistor radio's development' is the wordplay.
'origin of' indicates taking the first letters.
'development' indicates an anagram.
The first letter of 'transistor' is 't'.
't'+'radio'='tradio'
'tradio' with letters rearranged gives 'ADROIT'.
'in' is the link.
(Other definitions for adroit that I've seen before include "To raid (anag)" , "Canny" , "Dextrous" , "Deft and proficient" , "Quick and deft" .)