Tread he replaced and made safe (7)
I believe the answer is:
earthed
'made safe' is the definition.
Although both the answer and definition are past participle verbs, I don't see how one could define the other.
'tread he replaced' is the wordplay.
'replaced' indicates an anagram.
'tread'+'he'='treadhe'
'treadhe' is an anagram of 'EARTHED'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for earthed that I've seen before include "grounded" , "protected from shock" , "attached to the ground" .)