The endless corrosion brings forceful motivation (6)
I believe the answer is:
thrust
'forceful motivation' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'the endless corrosion' is the wordplay.
'endless' means to remove the last letter.
'corrosion' becomes 'rust' (rust is a kind of corrosion).
'the' with its last letter taken away is 'th'.
'th'+'rust'='THRUST'
'brings' acts as a link.
Can you help me to learn more?
(Other definitions for thrust that I've seen before include "Lunge forward" , "Sudden lunge or attack" , "Push suddenly and violently" , "Push forcefully" , "Push forward as with fencing sword" .)