The most common and most likely answer to this crossword clue is the 3 plus 3 letter word PEN NIB
I've seen this crossword clue in Independent
P
E
N
N
I
B
More clues leading to the result PEN NIB
Buddy explains!

The straight part
We know that "writer’s tip" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case writer’s tip = pen nib.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.