Redeem against silver found in auction (7)
I believe the answer is:
salvage
'redeem' is the definition.
(thesaurus)
'against silver found in auction' is the wordplay.
'against' becomes 'v' (versus).
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'found in' indicates putting letters inside.
'auction' becomes 'sale' (type of sale).
'v'+'ag'='vag'
'vag' put inside 'sale' is 'SALVAGE'.
(Other definitions for salvage that I've seen before include "Rescue (and recycle?)" , "Rescued sunken cargo" , "Recover discarded material" , "Rescue of goods from peril" , "Reclaim" .)