The most common and most likely answer to this crossword clue is the 4 plus 3 letter word YOLK SAC
I've seen this crossword clue in The Times
Y
O
L
K
S
A
C
More clues leading to the result YOLK SAC
- Bag for yellow sock lay abandoned
- Barrel old US actress tipped over, its contents yellow
- Mum’s food parcel – 50 kilograms – in a cosy bundle
- For starters, Yoko Ono likes kippers — she also coddles some egg
- “The young get nutrients from this cola” — Sky broadcast
- Mother shunned mayo: badly lacks some egg
- Auditor’s tyranny starts to suffocate all caretakers providing life support
Buddy explains!
The straight part
We know that "its contents yellow" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case its contents yellow = yolk sac.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.