Tudor queen (4)
I believe the answer is:
'tudor queen' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mary that I've seen before include "a religious icon" , "See 2" , "feature of 21/23 [NATIVITY SCENE]" , "Disney film with Julie Andrews" , "O'Rourke, Harney and McAleese" .)