Little chap beginning to thrive before long (5)
I believe the answer is:
Here is my best explanation:
'little chap' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'beginning to thrive before long' is the wordplay.
'beginning to' says to take the initial letters.
'before' means one lot of letters go next to another.
'long' becomes 'itch' (I've seen this before).
The first letter of 'thrive' is 't'.