The most common and most likely answer to this crossword clue is the 5 letter word CROON
C
R
O
O
N
Buddy explains!

The straight part
We know that "of those that do" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case of those that do = croon.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 CROON mean?
CROON noun- A soft or sentimental hum or song.
- To hum or sing softly or in a sentimental manner.
- To say softly or gently
- To soothe by singing softly.
- To make a continuous hollow moan, as cattle do when in pain.