Like a market sometimes, one about to offer precious metals (7)
I believe the answer is:
bullion
'precious metals' is the definition.
(thesaurus)
'like a market sometimes one about' is the wordplay.
'like a market sometimes' becomes 'bull' (bull market is a kind of market).
'one' becomes 'I' (Roman numeral).
'about' becomes 'on' (as in a book 'on' a certain topic).
'bull'+'i'+'on'='BULLION'
'to offer' acts as a link.
(Other definitions for bullion that I've seen before include "Bars of precious metal" , "Gold or silver in bulk" , "Precious metal in mass" , "Gold or silver in bars or ingots" , "Gold/silver in bulk" .)