Sign of hesitation over a long period (3)
I believe the answer is:
era
'long period' is the definition.
(I've seen this in another clue)
'sign of hesitation over a' is the wordplay.
'sign of hesitation' becomes 'er' ().
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'er'+'a'='ERA'
(Other definitions for era that I've seen before include "A particular period of time" , "Significant time" , "Long historical period" , "generation, maybe" , "Period, age" .)