Finished on time, it's not concealed (5)
I believe the answer is:
overt
'not concealed' is the definition.
(I've seen this before)
'finished on time' is the wordplay.
'finished' becomes 'over' (over can mean finished or ended).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'time' becomes 't' (abbreviation).
'over'+'t'='OVERT'
'it's' acts as a link.
(Other definitions for overt that I've seen before include "Done in an obvious way" , "Open, up front" , "Not concealed - public" , "Open and obvious" , "Conspicuous" .)