Adept corrected welcomes new stickler (6)
I believe the answer is:
pedant
'stickler' is the definition.
(I've seen this in another clue)
'adept corrected welcomes new' is the wordplay.
'corrected' indicates anagramming the letters.
'welcomes' indicates putting letters inside (in sense of 'invites in').
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'adept' is an anagram of 'pedat'.
'pedat' going around 'n' is 'PEDANT'.
(Other definitions for pedant that I've seen before include "Academically fussy person" , "Person who pays undue attention to the rules" , "One excessively concerned with minor detail" , "Know-all who insists on strict observance of rules" , "quibbler" .)