The most common and most likely answer to this crossword clue is the 9 letter word REFLECTED
I've seen this crossword clue in The Daily Telegraph
R
E
F
L
E
C
T
E
D
Buddy explains!
The straight part
We know that "Mused/sent back" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mused/sent back = reflected.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 REFLECTED mean?
REFLECTED verb- To bend back (light, etc.) from a surface.
- To be bent back (light, etc.) from a surface.
- To mirror, or show the image of something.
- To be mirrored.
- To agree with; to closely follow.
- To give evidence of someone's or something's character etc.
- To think seriously; to ponder or consider.
- Bent or sent back (especially of incident sound or light)