Vintage producer Selznick’s last about which we remain crazy (9)

'vintage producer' is the definition.
(a winemaker makes wines with a vintage)

'selznick's last about which we remain crazy' is the wordplay.
'last' indicates one should take the final letters.
'about which' is an insertion indicator (some letters go about or around others).
'crazy' indicates an anagram.
The final letter of 'selznick' is 'k'.
'we'+'remain'='weremain'
'weremain' with letters rearranged gives 'winemaer'.
'k' inserted inside 'winemaer' is 'WINEMAKER'.