Hallowed ground: can’t cross over area (10)
I believe the answer is:
sacrosanct
'hallowed' is the definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?
'ground can't cross over area' is the wordplay.
'ground' is an anagram indicator ('grind' the letters into a new form).
'over' means one lot of letters goes inside another.
'area' becomes 'a' (maths abbreviation).
'cant'+'cross'='cantcross'
'cantcross' is an anagram of 'sacrosnct'.
'sacrosnct' enclosing 'a' is 'SACROSANCT'.
Can you help me to learn more?
(Other definitions for sacrosanct that I've seen before include "Unchallengeable" , "Too valuable to touch" , "Inviolable" , "Too important to touch" , "Co-stars can (anag.)" .)