Formerly cone-shaped (4)
I believe the answer is:
once
'formerly' is the definition.
(I know that formerly can be written as once)
'cone-shaped' is the wordplay.
'shaped' indicates anagramming the letters.
'cone' with letters rearranged gives 'ONCE'.
(Other definitions for once that I've seen before include "In the old days" , "'... bitten, twice shy'" , "Formerly; as soon as" , "Formerly - not repeated" , "A single time" .)