Long post about a stockpile (5)
I believe the answer is:
cache
'a stockpile' is the definition.
(I've seen this in another clue)
'long post about' is the wordplay.
'long' becomes 'ache' (to long for something is to ache for it).
'post' is a charade indicator (letters next to each other) (post- can mean after).
'about' becomes 'c' (circa).
'ache' after 'c' is 'CACHE'.
(Other definitions for cache that I've seen before include "memory" , "Secretly keep" , "Reserve" , "Hiding place for treasure etc" , "Something hidden" .)