The answer is "elide"
It's one of those where it depends on which dictionary you use !!
Try AskOxford.com and you will get:
• verb 1 omit (a sound or syllable) when speaking. 2 join together; merge
Whether that makes it a good clue or not is, obviously, debatable. As most crossword puzzlers know, Chambers is the favourite reference for most compilers, and many definitions given in there are not to be found elsewhere.