Crossword puzzle clue "mark placed over short vowels"

an obsolescent musical note, twice as long as the longest now generally used (the semibreve)

DIERESIS, (Greek) the separation of two vowels into two syllables

to strike out (a word or passage)

ELIDE, to strike out (a word or passage)

MACRON, (Greek) a symbol placed over a vowel to indicate a long sound

to become like a jelly