Generous sort welcoming writer in Whetstone? (9)
I believe the answer is:
sharpener
'whetstone?' is the definition.
(thesaurus)
'generous sort welcoming writer' is the wordplay.
'generous sort' becomes 'sharer' (I've seen this in another clue).
'welcoming' is an insertion indicator (in sense of 'inviting in').
'writer' becomes 'pen' (something which writes).
'sharer' placed around 'pen' is 'SHARPENER'.
'in' is the link.
(Other definitions for sharpener that I've seen before include "in which The Edge improves?" , "Knife or pencil improver" , "one may make a point" , "that's wielded to make a point?" , "type of pointer?" .)