Rescue first piece of valuable silver put into auction (7)
I believe the answer is:
salvage
'rescue' is the definition.
(salvage is a kind of rescue)
'first piece of valuable silver put into auction' is the wordplay.
'first piece of' indicates taking the first letters.
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'put into' indicates putting letters inside.
'auction' becomes 'sale' (I've seen this before).
The first letter of 'valuable' is 'v'.
'v'+'ag'='vag'
'vag' placed within 'sale' is 'SALVAGE'.
(Other definitions for salvage that I've seen before include "Save - junk" , "Restore" , "Goods saved from wrecked ship" , "Retrieve goods from wrecked ship" , "Rescue of goods from peril" .)