The most common and most likely answer to this crossword clue is the 5 letter word LARVA
L
A
R
V
A
More clues leading to the result LARVA
- Caterpillar, for example, in popular variety
- Immature form of life right in centre of volcanic discharge
- Grub right inside burning liquid
- A bible in US city for bookworm, perhaps
- Rising sea overwhelms very immature creature
- Life form of some peculiar variety
- Add last of ginger to hot liquid, that's immature!
- Early form of atrioventricular valve
- Perhaps Caterpillar tractor’s rear trapped in rock
- Some popular variety of grub
Buddy explains!

The straight part
We know that "Baby bug" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case baby bug = larva.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 LARVA mean?
LARVA noun- An early stage of growth for some insects and amphibians, in which after hatching from their egg, insects are wingless and resemble a caterpillar or grub, and amphibians lack limbs and resemble fish.
- An animal in the aforementioned stage.
- A form of a recently born or hatched animal that is quite different from its adult stage.