It's a wonder Biblical figure blocks sink up (7)
I believe the answer is:
pyramid
'it's a wonder' is the definition.
(the Great Pyramid of Giza is a wonder of the world)
'biblical figure blocks sink up' is the wordplay.
'biblical figure' becomes 'Mary' (mother of Jesus).
'blocks' is an insertion indicator (the inside letters form a 'blockage').
'sink' becomes 'dip' (synonyms).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'mary' placed within 'dip' is 'dimaryp'.
'dimaryp' written backwards gives 'PYRAMID'.
(Other definitions for pyramid that I've seen before include "Monumental Egyptian structure" , "Egyptian stone structure" , "Form of ancient Egyptian royal tomb" , "Giza monument" , "Egyptian edifice" .)