The phrase "a speech explaining" is correct and usable in written English.
It can be used when referring to a speech that provides clarification or details about a specific topic.
Example: "The professor delivered a speech explaining the complexities of climate change and its impact on global ecosystems."
Alternatives: "a talk clarifying" or "a presentation detailing".
He prepared a speech explaining why, but he was absent on the day of the vote.
"Some thought I was dead," Mr. Pacquiao said in a speech explaining his vote against the measure.
Conroy resigned from the Senate on Thursday evening, tabling a speech explaining that he did so for family reasons.
There was a speech explaining all of this – a decent character note for making sense of everything else.
The plotters would crash nine of them, and Mohammed would triumphantly land the tenth, disembark, and give a speech explaining what he had done and why.
In a speech explaining the ministerial changes, Mr Tusk spoke tellingly of the need to spend EU funds with "dynamic activity".
Chancellor gives a long speech explaining how a chieftain in a native tribe rebelled against the white men and paid a violent price for it, inspiring Chancellor to accommodate himself to the new reality and throw his lot in with the men with power — which is to say the guns, as opposed to spears.
Less controversially a year ago he gave a big speech explaining his beliefs ("politics without values is sheer pragmatism") to the Christian Socialist Movement, long unfashionable until the late John Smith quietly confirmed his own active Presbyterianism.
Administration officials say that a strong speech explaining Mr. Obama's strategy for achieving success would provide them with fresh ammunition to galvanize support in foreign capitals.
In unprecedented scenes in the House of Commons, the Shadow Foreign Secretary received rapturous applause from MPs from across the House as he made a powerful speech explaining why he disagreed with his leader.
Hezbollah chief Hassan Nasrallah, in a 2013 speech explaining Hezbollah's intervention to prevent the fall of the Assad regime, described Syria as "the backbone of the resistance," referring to its pivotal role in supporting the organization.
