Miss, once dead, oddly forgotten (4)
I believe the answer is:
need
'miss' is the definition.
(I've seen this before)
'once dead oddly forgotten' is the wordplay.
'oddly forgotten' means one should take alternating letters (odd-numbered letters get removed).
'once'+'dead'='oncedead'
The alternating letters of 'oncedead' are 'NEED'.
(Other definitions for need that I've seen before include "Penury" , "Exigency" , "''A friend in .... is a friend indeed''" , "Rely on" , "Require; want" .)