Material spiked is put back (8)
I believe the answer is:
replaced
'is put back' is the definition.
(I've seen this before)
'material spiked' is the wordplay.
'material' becomes 'rep' (rep is a kind of material).
'spiked' becomes 'laced' ('lace' can be a synonym of 'spike').
'rep'+'laced'='REPLACED'
(Other definitions for replaced that I've seen before include "Led caper (anag.)" , "Substituted, supplanted" , "Put back in position" , "Substituted, exchanged" .)