Expert on game reveres Alison Mitchell's masterful elucidation primarily in Test Match Special ? (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

PRO (short for professional = expert), then initial letters (primarily) of G [ame] R [everes] A [lison] M [itchell’s] M [asterful] E [lucidation]. Definition by example: Test Match Special is the BBC’s cricket commentary radio programme, and Alison Mitchell is one of its regular commentators.