Sponsor new op art collection (6)
I believe the answer is:
patron
'sponsor' is the definition.
(I know that sponsor can be written as patron)
'new op art collection' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'collection' indicates an anagram (the same collection of letters).
'n'+'op'+'art'='nopart'
'nopart' anagrammed gives 'PATRON'.
(Other definitions for patron that I've seen before include "Regular customer; backer" , "Patrick for Ireland, for example" , "Regular customer or sponsor" , "manager (13) [FRENCH]" , "Restaurant customer" .)