Things that protect half-dead barriers (8)
I believe the answer is:
defences
'things that protect' is the definition.
Although both the answer and 'things' are nouns, they are not in the same form of the noun.
'half-dead barriers' is the wordplay.
'half' means to take half the letters.
'barriers' becomes 'fences' (fence is a kind of barrier).
'dead' halved is 'de'.
'de'+'fences'='DEFENCES'
Can you help me to learn more?
(Other definitions for defences that I've seen before include "ramparts?" , "barricades" , "legal cases for those charged" , "Means of protection" , "Protections or justifications" .)