Moved set piles of letters (8)
I believe the answer is:
epistles
'letters' is the definition.
(I know this)
'moved set piles' is the wordplay.
'moved' indicates anagramming the letters.
'set'+'piles'='setpiles'
'setpiles' anagrammed gives 'EPISTLES'.
'of' is the link.
(Other definitions for epistles that I've seen before include "Letters, missives" , "Biblical letters" , "It sleeps among letters of the Apostles" , "Long communications" .)