Treating initial corrosion provides confidence (5)
I believe the answer is:
trust
'confidence' is the definition.
(I know that confidence can be written as trust)
'treating initial corrosion' is the wordplay.
'initial' says to take the initial letters.
'corrosion' becomes 'rust' (rust is a kind of corrosion).
The initial letter of 'treating' is 't'.
't'+'rust'='TRUST'
'provides' acts as a link.
(Other definitions for trust that I've seen before include "Rely on" , "Hope, expect" , "Accept reliability of" , "Believe" , "Firm belief (in another)" .)