Regular figure, old-fashioned type (6)
I believe the answer is:
square
I believe this clue is a double definition.
'regular figure' is the first definition.
(I've seen this before)
'old-fashioned type' is the second definition.
(square can mean a boringly conventional person)
(Other definitions for square that I've seen before include "New York Times, for example" , "Eg, 4, 49 or 121" , "See 19" , "Sixteen, maybe" , "Old fogey" .)