Broadcaster on eastern part of Scotland (4)
I believe the answer is:
skye
'part of scotland' is the definition.
(I've seen this before)
'broadcaster on eastern' is the wordplay.
'broadcaster' becomes 'sky' (Sky is a broadcast TV channel).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'eastern' becomes 'e'.
'sky'+'e'='SKYE'
(Other definitions for skye that I've seen before include "Largest isle of the Inner Hebrides" , "Scottish isle" , "Home of the Cuillin mountains" , "Scots isle" , "Isle; terrier type" .)