Material produced in New York City reduced by 50 per cent (5)
I believe the answer is:
nylon
'material' is the definition.
(nylon is a kind of material)
'new york city reduced by 50 per cent' is the wordplay.
'new york' becomes 'ny'.
'city' becomes 'LA' (Los Angeles).
'reduced by 50' means to take half the letters (50 percent of the word is removed).
'per cent' becomes 'on' (I can't justify this - if you can you should give a lot more credence to this answer).
'la' cut in half is 'l'.
'ny'+'l'+'on'='NYLON'
'produced in' is the link.
Can you help me to learn more?
(Other definitions for nylon that I've seen before include "Tough synthetic material" , "Man-made fibre" , "Type of material" , "Tights material" , "The first synthetic fibre" .)