Hint that’s left in something needed by Potter (4)
I believe the answer is:
clue
'something needed by potter' is the definition.
I can't tell whether this definition defines the answer.
'hint that's left in' is the wordplay.
'hint' becomes 'cue' (I've seen this in another clue).
'that's left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'cue' placed around 'l' is 'CLUE'.
Can you help me to learn more?
(Other definitions for clue that I've seen before include "It's here top be solved" , "crossword guide" , "Crossword aid" , "Hint to help the puzzler" , "Hint, tip" .)