Sentence:  On the one hand, it is unwise, by granting ‘<WSD>flextension</WSD>', for the European Council to allow itself to be blamed for trapping the UK inside the Union against the expressed will of the British people to leave it. 
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).