Former coin (6)
(Other definitions for florin that I've seen before include "Old English coin worth 10p" , "Former English coin" , "Old two-shilling piece" , "Old two-shilling-piece" , "Old 2-shilling coin" .)
'former coin' is the definition.
(historical type of coin)
This is the entire clue.
(Other definitions for guinea that I've seen before include "Country -- 21 shillings" , "Former gold coin" , "Old coin worth 21 shillings" , "so-called pig that's experimentally tested?" , "country - or new?" .)
(Other definitions for sixpence that I've seen before include "Old coin worth two and a half new pence" , "Old British coin" , "bit dated" , "Old tanner" , "Sing a Song of one" .)
(Other definitions for shilling that I've seen before include "Old piece" , "Bob" , "Old unit of imperial money, worth 12 pence" , "Pre-decimalisation coin" , "Until 1971, ready here" .)