Current inside Neptunian satellite, after a time, is wearing down (9)
I believe the answer is:
attrition
'is wearing down' is the definition.
(thesaurus)
'current inside neptunian satellite after a time' is the wordplay.
I cannot quite see how this works, but
'current' could be 'i' (symbol for electric current) and 'i' is present in the answer.
'satellite' could be 'io' (Io is a moon of Jupiter) and 'io' is found in the answer.
'a' is within the answer.
'time' could be 't' (abbreviation) and 't' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for attrition that I've seen before include "Wearing down of enemy" , "Constant wearing down - it ain't rot (anag)" , "Wearing down - natural wastage" , "Grinding down" , "Process of gradually wearing down" .)