The most common and most likely answer to this crossword clue is the 7 letter word MARCONI
I've seen this crossword clue in The Daily Telegraph
M
A
R
C
O
N
I
More clues leading to the result MARCONI
- Fixing car, I’m no expert on radio!
- Italian physicist taking brandy on island
- Telegraph man appearing to interrupt one runner-up
- Italian physicist has abandoned Minorca
- Engineer to study electrical current after damage
- Return stuff about India’s dead Nobel laureate
- He had signal success at the end of the nineteenth century
- Engineer setting stuff up, the operating electrical current
- Polo ponies’ centre supplying famous Italian
- Radio producer Mike bowed before new leader of Indonesia
Buddy explains!
The straight part
We know that "First broadcaster" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case first broadcaster = marconi.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.