The most common and most likely answer to this crossword clue is the 4 letter word YOLK
I've seen this crossword clue in The Times
Y
O
L
K
More clues leading to the result YOLK
- Not the white team, we hear
- Food kept by white couple, you might say
- Bird food in city changing hands
- Yellow tie at audition
- Cook loyally holds back part of egg
- The yellow tie mentioned
- We’re told to put together basic bird food
- Something for soldiers to dip into, if not hard boiled
- Burden, we hear, is something attractive to soldiers?
- Sounds burdensome, could be soft for soldiers
Buddy explains!

The straight part
We know that "Yellow" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case yellow = yolk.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 YOLK mean?
YOLK noun- The yellow, spherical part of an egg that is surrounded by the white albumen, and serves as nutriment for the growing young.
- The grease in a sheep's fleece.