phrasal verb

可能是
Under my sleeve吧？

意思是我所不為人知的技能或未顯露或使出的手段-引自魔術師從袖中抽出東西變法。

I don't think there is such a phrasal verb. Neither is it found in the dictionaries nor on the Internet.
There are phrases like:
be in leaf/ come into leaf = have or start growing leaves at a particualr time or year.
e.g. The forest was just coming into leaf.
take a leaf out of somebody's book = to copy the way someone else behaves because you want to be like them or be as successful as they are.
e.g. They are committing $3 million to research. We could take a leaf out of their book.
turn over a new leaf = to change the way you behave and become a better person.
e.g. I see fatherhood as a chance to turn over a new leaf.