Mean to declare silver necklace ultimately (7)
I believe the answer is:
average
'mean' is the definition.
('average' can be a synonym of 'mean')
'declare silver necklace ultimately' is the wordplay.
'declare' becomes 'aver' (averring is a kind of declaring**).
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'ultimately' indicates one should take the final letters.
The final letter of 'necklace' is 'e'.
'aver'+'ag'+'e'='AVERAGE'
'to' acts as a link.
(Other definitions for average that I've seen before include "Mediocre, commonplace" , "Normal amount" , "Mediocre - medium" , "Mean figure?" , "Usual - mediocre - mean" .)