Loud workmen I’d recast in radio play (5,4,4)
I believe the answer is:
under milk wood
Here is my best explanation:
'radio play' is the definition.
(I've seen this before)
'loud workmen i'd recast' is the wordplay.
'recast' indicates anagramming the letters.
'loudworkmenid' is an anagram of 'UNDER MILK WOOD'.
'in' acts as a link.
(Other definitions for under milk wood that I've seen before include "Work by Dylan Thomas", "Welsh play", "Fail fully to exploit deal", "Radio play by Dylan Thomas", "radio play", "Dylan Thomas work", "Radio poem by Dylan Thomas" and "Play".)