Depend on finding corrosion on a historic model car (5)
I believe the answer is:
trust
'depend on' is the definition.
(I've seen this in another clue)
'corrosion on a historic model car' is the wordplay.
'corrosion' becomes 'rust' (rust is a kind of corrosion).
'on' means one lot of letters go next to another.
'a historic model car' becomes 't' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rust' put after 't' is 'TRUST'.
'finding' is the link.
Can you help me to learn more?
(Other definitions for trust that I've seen before include "Firm belief (in someone)" , "Firm belief (in person)" , "Place confidence in or reliance on" , "'Put your . . . . . In God, and keep your powder dry'" , "Firm belief (in a thing)" .)