Letter I left in printer? (7)
I believe the answer is:
epsilon
'letter' is the definition.
(I know that epsilon is a type of letter)
'i left in printer?' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'printer?' becomes 'epson' (I am not sure about this - if you are sure you should believe this answer much more).
'i'+'l'='il'
'il' going into 'epson' is 'EPSILON'.
Can you help me to learn more?
(Other definitions for epsilon that I've seen before include "Foreign character" , "Greek letter - pinoles (anag)" , "5th letter of the Greek alphabet" , "Fifth brightest star in a constellation" , "small number mispronounced, almost completely the wrong way round" .)