Left oily rag in trash initially (10)
I believe the answer is:
originally
'initially' is the definition.
(thesaurus)
'left oily rag in trash' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'al' (I've seen this in other clues) and 'al' is found in the answer.
'in' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for originally that I've seen before include "to begin with" , "In the first place" , "At the start" , "new way" .)