J M —, author of 1907 stage play The Playboy of the Western World (5)
I believe the answer is:
synge
(Other definitions for synge that I've seen before include "Irish poet and playwright, d. 1909" , "J. M. --, Irish dramatist" , "John Millington . . . . ., great Irish playwright" , "John Millington . . . . . wrote 'The Playboy of the Western World'" , "J. M. --, Irish poet/playwright" .)