Full stop (6)
'full stop' is the definition.
(US name for a full stop)
This is the entire clue.
(Other definitions for period that I've seen before include "Phase" , "Stretch - cycle" , "Era, epoch" , "End of story" , "Amount of time - US full stop" .)
(Other definitions for kibosh that I've seen before include "Rubbish - nonsense" , "Fatal to put this on" , "Put the ___ on - rubbish" , "Put this on something and stop it from happening" , "Terminate" .)