Free stamp (5)
I believe the answer is:
frank
I believe this is a double definition.
'free' is the first definition.
(to speak frankly is to speak freely)
'stamp' is the second definition.
(I know that frank is a more specific form of stamp)
(Other definitions for frank that I've seen before include "Candid, honest" , "Anne ---, diarist" , "Open" , "Outspoken" , "Without evasion" .)