Mistakenly agrees to provide lubricant (6)
I believe the answer is:
grease
'lubricant' is the definition.
(I've seen this before)
'mistakenly agrees' is the wordplay.
'mistakenly' is an anagram indicator.
'agrees' is an anagram of 'GREASE'.
'to provide' acts as a link.
(Other definitions for grease that I've seen before include "Fat, film" , "Mechanic (informal)" , "Rock musical" , "bribe" , "A thick oily substance" .)