Black cat's first monument (4)
I believe the answer is:
tomb
'monument' is the definition.
(I know that tomb is a type of remembrance)
'black cat's first' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'cat' becomes 'tom' (a tom is a male cat).
'first' means one lot of letters go next to another.
'b' after 'tom' is 'TOMB'.
(Other definitions for tomb that I've seen before include "remains here" , "Place of burial, grave or vault" , "Sepulchral monument" , "Place for the burial of a corpse" , "grave situation" .)