telltale
adjective /ˈtelteɪl/
  /ˈtelteɪl/
[only before noun]- showing that something exists or has happened
- telltale clues/marks/signs/sounds
 - The telltale smell of cigarettes told her that he had been in the room.
 
Oxford Collocations DictionaryTelltale is used with these nouns:- sign
 - signature