Put one's name on placard (4)
I believe the answer is:
sign
I believe this clue is a double definition.
'put one's name on' is the first definition.
'placard' is the second definition.
(thesaurus)
(Other definitions for sign that I've seen before include "Evidence" , "Public display of a message" , "Autograph" , "Ram" , "Omen or indication" .)