A mature sort of dabbler (7)
I believe the answer is:
amateur
'dabbler' is the definition.
(thesaurus)
'a mature sort' is the wordplay.
'sort' is an anagram indicator.
'mature' with letters rearranged gives 'mateur'.
'a'+'mateur'='AMATEUR'
'of' is the link.
(Other definitions for amateur that I've seen before include "incompetent" , "Unpaid or unskilled" , "lacking professionalism" , "refusing payment" , "He's not professional" .)