Bob twice gets this old piece of silver (6)
I believe the answer is:
florin
This clue might be a double definition.
'bob' is the first definition.
(thesaurus)
'twice gets this old piece of silver' is the second definition.
'florin' can be an answer for 'old piece of silver'. I'm not sure about the rest of the definition.
(Other definitions for florin that I've seen before include "Old English coin worth 10p" , "Old two-bob bit" , "An old two-shilling coin" , "Old two-shilling piece" , "ten pence" .)