Bairn troubled with insect around is a "weed” (8)

'a weed' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'bairn troubled with insect around is' is the wordplay.
'troubled' indicates anagramming the letters.
'with' says to put letters next to each other.
'insect' becomes 'e' (I can't explain this - if you can you should give a lot more credence to this answer).
'around' means one lot of letters goes inside another.
'is' becomes 'be'.
'bairn' anagrammed gives '[bairn]'.
'[bairn]'+'e'='arbine'
'arbine' placed around 'be' is 'BEARBINE'.

Can you help me to learn more?