Attract newlywed to cross key part of castle, perhaps (10)
I believe the answer is:
drawbridge
'part of castle perhaps' is the definition.
(a castle might have a drawbridge)
'attract newlywed to cross key' is the wordplay.
I cannot really understand how this works, but
'attract' could be 'draw' (synonyms) and 'draw' is located in the answer.
'cross' could be 'bridge' (bridging is a kind of crossing) and 'bridge' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for drawbridge that I've seen before include "Keep attachment" , "for reasons of security" , "Barbican may defend this" , "One may protect castle" , "Castle defence" .)