End fuel production, as required (7)
I believe the answer is:
needful
'required' is the definition.
(I know that required can be written as needful)
'end fuel production' is the wordplay.
'production' indicates an anagram.
'end'+'fuel'='endfuel'
'endfuel' anagrammed gives 'NEEDFUL'.
'as' is the link.
(Other definitions for needful that I've seen before include "poor" , "Requisite, necessary" , "Required" , "Necessary for nude elf" , "Nude elf (anag.)" .)