Old coin displayed by gallery in empty salver (6)
I believe the answer is:
stater
'old coin' is the definition.
(I've seen this before)
'gallery in empty salver' is the wordplay.
'gallery' becomes 'tate' (I've seen this before).
'in' is an insertion indicator.
'empty' suggests removing the centre.
'salver' with its centre removed is 'sr'.
'tate' placed within 'sr' is 'STATER'.
'displayed by' acts as a link.
(Other definitions for stater that I've seen before include "One specifying" , "One expressing clearly; ancient Greek coin" , "Old Greek coin" , "I say" , "He says" .)