Amateur (6)
(Other definitions for rookie that I've seen before include "untested type" , "Army or police recruit" , "New (police) recruit (colloq.)" , "Slang for a new recruit" , "inexperienced fighter" .)
'amateur' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for novice that I've seen before include "Beginner, trio" , "A beginner or student nun" , "Beginner, perhaps at religious orders" , "Probationary nun/monk" , "Beginner as in religious order" .)
'amateur' is the definition.
(a layman is an amateur or non-expert)
This is the entire clue.
(Other definitions for layman that I've seen before include "He's not clergy or military" , "He's not a priest or specialist" , "He's not ordained or professional" , ""nonspecialist"" , "Non-ordained church member" .)
'amateur' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for lay that I've seen before include "Narrative poem" , "Unprofessional" , "Put down (eg, card)" , "Of bird, produce egg" , "Secular; set" .)
'amateur' is the definition.
(I know that dilettante is a type of amateur)
This is the entire clue.
(Other definitions for dilettante that I've seen before include "Aesthete" , "Superficial art-lover" , "amateur artist" , "whose study is superficial?" , "One dabbling" .)