Time worth studying (3)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
era
'time worth studying' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for era that I've seen before include "Age of importance" , "Period of alteration" , "8" , "Long period of history" , "A particular period of time" .)