The bolivar exchanged for a biscuit (4,6)
I believe the answer is:
bath oliver
'a biscuit' is the definition.
(I've seen this before)
'the bolivar exchanged' is the wordplay.
'exchanged' indicates anagramming the letters.
'the'+'bolivar'='thebolivar'
'thebolivar' is an anagram of 'BATH OLIVER'.
'for' is the link.
(Other definitions for bath oliver that I've seen before include "Hard cheese biscuit - a live throb (anag)" , "Plain type of biscuit" .)