Actor Dern (5)
I believe the answer is:
bruce
'actor dern' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bruce that I've seen before include "Robert the -; Lenny -" , "Robert the -, Scots king" , "Allied group of countries" , "-- Forsyth; -- Willis" , "Scottish boy's name" .)