The most common and most likely answer to this crossword clue is the 3 letter word REG
I've seen this crossword clue in The Guardian
R
E
G
Buddy explains!

The straight part
We know that "Elton John to his mother," is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case elton john to his mother, = reg.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 REG mean?
REG noun- A regular.
- A regulation.
- Registrar
- Registration
- Registry
- A hard surface of rock fragments set in a sandy matrix, found in some hot deserts; regolith, stony desert.