Engineer examined such a dramatic device (4,2,7)
I believe the answer is:
deus ex machina
'dramatic device' is the definition.
(type of narrative device)
'engineer examined such a' is the wordplay.
'engineer' is an anagram indicator.
'examined'+'such'='examinedsuch'
'examinedsuch' is an anagram of 'deusexmachin'.
'deusexmachin'+'a'='DEUS EX MACHINA'
(Other definitions for deus ex machina that I've seen before include "Unexpected problem solver" , "Happy-ending contrivance (Lat.)" , "Late delivery" , "An unlikely solution" , "unlikely device to resolve difficulty" .)