New Year bill at the end paid for by plastic (5)
I believe the answer is:
nylon
'plastic' is the definition.
(thesaurus)
'new year bill at the end paid for by' is the wordplay.
'new year' becomes 'ny' (abbreviation).
'at the end' suggests the final letters.
'paid for by' becomes 'on' (as in 'the drinks are on me').
The last letter of 'bill' is 'l'.
'ny'+'l'+'on'='NYLON'
(Other definitions for nylon that I've seen before include "Man-made fabric" , "Artific ial (stocking) material" , "Artificial cloth" , "The first synthetic fibre" , "Type of material" .)