Scottish surname starter (3)
I believe the answer is:
mac
'scottish surname starter' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mac that I've seen before include "Waterproof raincoat, in short" , "Waterproof coat (colloq.)" , "PC" , "laptop?" , "A Gaelic son, often in name" .)