Answer: persistent

AnswerCrossword Clue
PERSISTENTNot letting go
persistentlasting or permanent, as a physical trait
persistentcontinuing, as with a task, esp. in spite of obstacles
persistentconstantly repeated; continued
persistentpersisting, lasting / something that is persistent
persistentremaining attached beyond the usual time, as flowers or leaves
persistentlasting or enduring tenaciously