The most common and most likely answer to this crossword clue is the 4 letter word CLIO
I've seen this crossword clue in The Guardian
C
L
I
O
More clues leading to the result CLIO
- Muse about wild animal losing tail
- Primarily, clever lyrist inhabiting Olympus?
- She inspired historians starting to chart life in Oxford
- Inspiration taken from heraldic lion
- French model Nicole stripped for casting?
- Muse about painting from the east
- Muse about Greece heard on reflection
- Muse... 100 + 50 + 10
- Muse about animal having lost its tail
- Muse about painting that’s turned up
Buddy explains!

The straight part
We know that "source of inspiration for historian" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case source of inspiration for historian = clio.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.