Do her friends call her 'Bud'? (4)
I believe the answer is:
rosa
'do' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'her friends call her 'bud'?' is the wordplay.
I cannot quite see how this works, but
'her' could be 'ros' and 'ros' is located in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rosa that I've seen before include "Sub .... - in confidence" , "Parks" .)