Prisoner gets charge in certainty (10)
I believe the answer is:
conviction
'certainty' is the definition.
(I've seen this before)
'prisoner gets charge' is the wordplay.
'prisoner' becomes 'convict' (convict is a kind of prisoner).
'gets' means one lot of letters go next to another.
'charge' becomes 'ion' (an ion is a charged particle).
'convict'+'ion'='CONVICTION'
'in' is the link.
(Other definitions for conviction that I've seen before include "No doubt" , "Certainty" , "Strong belief" , "that may lead to imprisonment?" , "in being found guilty" .)