One of 78 in this puzzle (4)
I believe the answer is:
clue
'one of 78 in this puzzle' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for clue that I've seen before include "One indicates" , "crossword guide" , "Hint; piece of evidence" , "Slight indication (as here)" , "Hint to help the puzzler" .)