Jenny is about to see an oil source (7)
I believe the answer is:
linseed
'an oil source' is the definition.
(I've seen this before)
'jenny is about to see' is the wordplay.
I cannot quite see how this works, but
'to see' could be 'see' (seeing is a kind of seeing) and 'see' is located in the answer.
'jenny' could be 'lind' (19th-century actress Jenny Lind) and 'lind' is found within the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for linseed that I've seen before include "Type of oil" , "Oil-producing plant" , "Flax product, a source of oil" , "Part of flax used as oil" , "Flax plant product providing oil" .)