The most common and most likely answer to this crossword clue is the 4 letter word GILD
I've seen this crossword clue in The Times
G
I
L
D
Buddy explains!
The straight part
We know that "don't do this to Lily!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case don't do this to lily! = gild.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.
What does GILD mean?
GILD verb- To cover with a thin layer of gold; to cover with gold leaf.
- To adorn.
- To decorate with a golden surface appearance.
- To give a bright or pleasing aspect to.
- To make appear drunk.
- A group or association mainly of tradespeople made up of merchants, craftspeople, or artisans for mutual aid, particularly in the Middle Ages.
- A corporation.
- A group of diverse species that share common characteristics or habits.
- An organized group of players who regularly play together in a multiplayer game.