This uses initial letters - look for words whose first letters can be taken to spell something out.
Take the initial letters of 'Early telegraph cables' to get a common abbreviation, then connect it to the definition which asks for the full form of that abbreviation.
Answer: ET CETERA | The initial letters of 'Early telegraph cables' give you ETC, which is short for 'et cetera' - and the definition 'this' refers to the phrase itself (a common way to clue ET CETERA).