Starting telly is depressing: it normally gives sad news (7)
I believe the answer is:
tidings
'news' is the definition.
('tidings' can be a synonym of 'news')
'starting telly is depressing it normally gives sad' is the wordplay.
'starting' suggests taking the first letters.
The first letters of 'telly is depressing it normally gives sad' is 'TIDINGS'.
(Other definitions for tidings that I've seen before include "News, reports" , "Information about recent events" , "News (obs.)" , "News, information" , "News (arch.)" .)