Crossword puzzle clue "word that can appear before the starts of a b c d and e across crossword theme e g"

"Word that can appear before the starts of A-, B- C-, D- and E-Across" crossword theme, e.g.

First word across in the first-ever crossword (1913) and the first of a dozen appearances of the word in this puzzle's grid, written word search-style (left, right, down, and diagonally) ... Can you f

Parts of it appear at both the starts and ends of this puzzle's eight theme phrases

Actress/singer Helen with the CD "Crossword" (the title track starts "I found my true love today doing the crossword on the back of the 6 train")

Retail come-ons ... and what the starts of the longest Across answers can be?

Title that can precede the starts of the four longest Across answers