Style of architecture that may be dropped (13)
I believe the answer is:
perpendicular
'style of architecture' is the definition.
(perpendicular is a kind of style of architecture)
'may be dropped' is the wordplay.
I cannot quite understand how this works, but
'be' could be 'end' (ending is a kind of being) and 'end' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'that' is the link.
Can you help me to learn more?
(Other definitions for perpendicular that I've seen before include "Vertical; upright" , "At right angles" , "At ninety degrees" , "Sort of architecture" , "Style of late English Gothic church architecture" .)