On the subject of, more or less (5)
I believe the answer is:
about
I believe this is a double definition.
'on the subject of' is the first definition.
(I've seen this before)
'more or less' is the second definition.
('about' can be a synonym of 'more or less')
(Other definitions for about that I've seen before include "On the subject of, approximately" , "In the area of or in relation to" , "Approximately, or in vicinity" , "Concerning or around" , "Encompassing" .)