Uphold a try, if converted (6)
I believe the answer is:
ratify
'uphold' is the definition.
(thesaurus)
'a try if converted' is the wordplay.
'converted' is an anagram indicator.
'a'+'try'+'if'='atryif'
'atryif' with letters rearranged gives 'RATIFY'.
(Other definitions for ratify that I've seen before include "Authenticate" , "Formally consent to (treaty)" , "Affirm" , "OK" , "Sign or give formal consent" .)