Bar mitzvah, for one (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
rite
'bar mitzvah for one' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rite that I've seen before include "Solemn ceremony" , "Custom" , "Formal procedure" , "Uncomplaining person" , "form of service" .)