Impertinent teen left terrible impression (7)
I believe the answer is:
imprint
'terrible impression' is the definition.
'imprint' can be an answer for 'impression' (imprint is a kind of impression). I'm not certain of the 'terrible' bit.
'impertinent teen left' is the wordplay.
'left' suggests deleting specific letters (some letters have left).
'impertinent' with 'teen' taken away is 'IMPRINT'.
Can you help me to learn more?
(Other definitions for imprint that I've seen before include "Stamp; impression" , "Stamp; brand" , "Mark made by pressing or stamping surface" , "Publisher's name on title-page of book" , "make an impact" .)