The most common and most likely answer to this crossword clue is the 6 letter word CODING
I've seen this crossword clue in The Guardian
C
O
D
I
N
G
Buddy explains!
The straight part
We know that "What programmer does" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what programmer does = coding.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 CODING mean?
CODING verb- To write software programs.
- To add codes to a dataset.
- To categorise by assigning identifiers from a schedule, for example CPT coding for medical insurance purposes.
- To encode.
- To encode a protein.
- To call a hospital emergency code.
- Of a patient, to suffer a sudden medical emergency (a code blue) such as cardiac arrest.
- The process of encoding or decoding.
- The process of writing computer software code.
- An encoding.
- A method of communicating important medical information discreetly and quickly between medical professionals and responders.
- An alternative therapy used to treat addictions by convincing the patient (through hypnosis, placebos, etc.) that the substance will harm or kill them if they use it again.