The most common and most likely answer to this crossword clue is the 4 letter word EMIT
E
M
I
T
More clues leading to the result EMIT
Buddy explains!

The straight part
We know that "Send out" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case send out = emit.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 EMIT mean?
EMIT verb- To send out or give off