Sentence:  He has proposed a ‘<WSD>flextension'</WSD> – another new word to add to the Brexit lexicon – in which he proposes a year-long delay with the proviso that the UK can leave the EU as soon as Parliament agrees a deal. 
Meaning of the word marked with <WSD> tags:  The extension of a deadline that allows a flexible final date (originally used to refer to Brexit, but subsequently extended to other contexts).