Lots of oil here on fancy clothes (8)
I believe the answer is:
refinery
'lots of oil here' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'on fancy clothes' is the wordplay.
'on' becomes 're' (regarding).
'fancy clothes' becomes 'finery' (I've seen this before).
're'+'finery'='REFINERY'
Can you help me to learn more?
(Other definitions for refinery that I've seen before include "Factory which removes impurities etc from crude substances" , "Industrial installation where a substance is purified" , "Where oil is processed" , "Industrial processing plant (for, eg, oil)" , "Purification plant" .)