Machine shop alloy (6)
I believe the answer is:
solder
'machine shop alloy' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for solder that I've seen before include "Melted alloy, used to join two metal surfaces" , "Alloy melted to join circuit components" , "Join or fuse metal, using an alloy" , "Fusible jointing alloy" , "Join two metals with a melted alloy" .)