Ancient period's character captured by wise person (5,3)
I believe the answer is:
stone age
'ancient period's' is the definition.
(I've seen this in another clue)
'character captured by wise person' is the wordplay.
'character' becomes 'tone' (tone can mean a character or mood).
'captured by' means one lot of letters goes inside another.
'wise person' becomes 'sage' (sage can mean a wise or holy person).
'tone' inserted inside 'sage' is 'STONE-AGE'.
(Other definitions for stone age that I've seen before include "Early epoch when man used pre-metal tools" , "Neolithic" , "Hard time" , "before copper came in" , "Earliest known period of human culture" .)