Youngster finds hot stuff right inside (5)
I believe the answer is:
larva
'youngster' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'hot stuff right inside' is the wordplay.
'hot stuff' becomes 'lava' (I've seen this in another clue).
'right' becomes 'r' (common abbreviation).
'inside' is an insertion indicator.
'lava' enclosing 'r' is 'LARVA'.
'finds' is the link.
Can you help me to learn more?
(Other definitions for larva that I've seen before include "Immature stage of an insect" , "nit?" , "Early stage of creature" , "Grub, caterpillar stage" , "Insect's immature form" .)