The most common and most likely answer to this crossword clue is the 6 letter word KEYING
I've seen this crossword clue in The Guardian
K
E
Y
I
N
G
More clues leading to the result KEYING
Buddy explains!
The straight part
We know that "typist is doing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case typist is doing = keying.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.
What does KEYING mean?
KEYING verb- To fit (a lock) with a key.
- To fit (pieces of a mechanical assembly) with a key to maintain the orientation between them.
- To mark or indicate with a symbol indicating membership in a class.
- (telegraphy and radio telegraphy) To depress (a telegraph key).
- To operate (the transmitter switch of a two-way radio).
- (more usually to key in) To enter (information) by typing on a keyboard or keypad.
- To vandalize (a car, etc.) by scratching with an implement such as a key.
- To link (as one might do with a key or legend).
- To be identified as a certain taxon when using a key.
- To modify (an advertisement) so as to target a particular group or demographic.
- To attune to; to set at; to pitch.
- To fasten or secure firmly; to fasten or tighten with keys or wedges.
- In the sociology of Erving Goffman, an action or utterance that signals the meaning of interaction to participants.
- The input of text or data by means of a keyboard.
- A form of vandalism performed by scratching paint with a key