Children's author had tea with Orwell, finally (4)
I believe the answer is:
dahl
'children's author' is the definition.
(Roald Dahl)
'had tea with orwell finally' is the wordplay.
'finally' suggests the final letters.
The last letters of 'had tea with orwell' are 'DAHL'.
(Other definitions for dahl that I've seen before include "British writer notably of children's books" , "British author, notably of children's books, d.1990" , "Roald -, Br. author" , "Roald - - (deviser of Willy-Wonka)" , "'Roald ..., children's author (4)'" .)