Can it have to be proved? (5)
I believe the answer is:
shown
'be proved?' is the definition.
(thesaurus)
'can it have' is the wordplay.
'can it' becomes 'sh' ('can it' can mean stop talking or be quiet).
'have' becomes 'own' (synonyms).
'sh'+'own'='SHOWN'
'to' acts as a link.
(Other definitions for shown that I've seen before include "Explained" , "Demonstrated" , "Exhibited" , "Displayed" .)