Did something one day — about time! (5)
I believe the answer is:
acted
'did something' is the definition.
('act' can be a synonym of 'do something')
'one day about time' is the wordplay.
'one' becomes 'ace' (ace has a value of one in some card games).
'day' becomes 'd' (abbreviation for day).
'about' means one lot of letters goes inside another.
'time' becomes 't' (abbreviation).
'ace'+'d'='aced'
'aced' placed around 't' is 'ACTED'.
(Other definitions for acted that I've seen before include "Worked" , "Performed on stage" , "Behaved or played a part" , "exerted influence" , "Play a role" .)