The most common and most likely answer to this crossword clue is the 3 plus 4 letter word TEA TREE
I've seen this crossword clue in The Guardian
T
E
A
T
R
E
E
More clues leading to the result TEA TREE
- Source of oil on end of mantelpiece, alongside source of milk
- Plant husband chucked out of house with energy
- The matter here oddly refers to oil producer
- Hard to leave location of show by energy drink supplier
- Plays with wife, at last, when husband is out getting plant
- Treat freely — central need is for source of aromatic oil
Buddy explains!
The straight part
We know that "oil producer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case oil producer = tea tree.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.