Mark's small container of lube holds two gallons (7)
I believe the answer is:
speckle
'mark's' is the definition.
(thesaurus)
'small container of lube holds two gallons' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'container of' says to hollow out the word (remove centre letters).
'holds' means one lot of letters goes inside another.
'two gallons' becomes 'peck' (I can't explain this - if you can you should believe this answer much more).
'lube' with its centre taken out is 'le'.
's'+'le'='sle'
'sle' enclosing 'peck' is 'SPECKLE'.
Can you help me to learn more?
(Other definitions for speckle that I've seen before include "Bespatter" , "Small spot of colour" , "Small patch of colour" , "Small mark on skin" , "Little dot" .)