What's been written of oil spillage? (5)
I believe the answer is:
folio
'spillage?' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'what's been written of oil' is the wordplay.
'of oil' can be anagrammed to 'FOLIO'.
Though, I'm not sure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for folio that I've seen before include "Folded sheet - or book made from such" , "Leaf of paper" , "File" , "Manuscript sheet" , "large book" .)