Name torn from Chinese book chap pens — one of fifty (8)
I believe the answer is:
michigan
'one of fifty' is the definition.
(one of the 50 US states)
'name torn from chinese book chap pens' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'torn from' indicates named letters should be taken away.
'chinese book' becomes 'I Ching' (ancient Chinese text).
'chap' becomes 'Man' (chap can mean a man).
'pens' means one lot of letters goes inside another (to pen can mean to contain or imprison).
'iching' with 'n' taken out is 'ichig'.
'ichig' put within 'man' is 'MICHIGAN'.
(Other definitions for michigan that I've seen before include "US state and Great Lake" , "American state, capital Lansing" , "I'm aching to see American state" , "I'm aching to go to a Great Lake" , "I'm aching to go out the US state" .)