Dedicated (7)
There are a few possibilities for this:
single-minded
'dedicated' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for earnest that I've seen before include "Grave" , "Serious - money deposit" , "Serious, intent" , "Oscar Wilde wrote ''The importance of Being . . . . . . . '' (7)" , "Sincere; determined" .)
'dedicated' is the definition.
(synonyms)
This is all the clue.
(Other definitions for devoted that I've seen before include "Strongly attached (to)" , "Faithful" , "Loving and loyal" , "Dedicated or wholly given up to" .)
'dedicated' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for single-minded that I've seen before include "Concentrating on only one aim" , "Dedicated to one outcome" , "Not distracted from chosen purpose" , "Bent upon one sole purpose" , "Concentrating on one particular thing" .)