Oils, oddly, found in lots of treacle (8)
I believe the answer is:
molasses
'treacle' is the definition.
(thesaurus)
'oils oddly found in lots' is the wordplay.
'oddly' means one should take alternating letters.
'found in' means one lot of letters goes inside another.
'lots' becomes 'masses' ('mass' can be a synonym of 'lot'**).
The alternating letters of 'oils' are 'ol'.
'ol' put inside 'masses' is 'MOLASSES'.
'of' acts as a link.
(Other definitions for molasses that I've seen before include "Thick syrup extracted from sugar cane" , "Dark syrup from raw sugar" , "Black treacle" , "Thick dark treacle" , "Dark syrup extracted from sugar cane" .)