Clue originally featured in 1 — and never again? (4)
I believe the answer is:
once
'never again?' is the definition.
(once can mean one time only)
'clue originally featured in 1' is the wordplay.
'originally' says to take the initial letters.
'featured in' means one lot of letters goes inside another.
'1' becomes 'one' (synonyms).
The initial letter of 'clue' is 'c'.
'c' put inside 'one' is 'ONCE'.
'and' is the link.
(Other definitions for once that I've seen before include "in bygone era" , "not repeatedly" , "... upon a time for the storyteller" , "Formerly - not repeated" , "in bygone days" .)