Classic contest to acquire National Trust silver (7)
I believe the answer is:
vintage
'classic' is the definition.
(thesaurus)
'contest to acquire national trust silver' is the wordplay.
'contest' becomes 'vie' (I've seen this before).
'to acquire' means one lot of letters goes inside another.
'national trust' becomes 'nt'.
'silver' becomes 'ag' ('Ag' can be a synonym of 'silver').
'nt'+'ag'='ntag'
'vie' going around 'ntag' is 'VINTAGE'.
(Other definitions for vintage that I've seen before include "Wine of a particular year" , "High quality wine" , "Type of wine" , "Old" , "Wine of a good year" .)