Might allow unknown character to annoy them (6)
I believe the answer is:
nettle
'unknown character to annoy them' is the definition.
I can't tell whether this definition defines the answer.
'might allow' is the wordplay.
'might' becomes 'nett' (I can't explain this - if you can you should believe this answer much more).
'allow' becomes 'le' (I've seen this in other clues).
'nett'+'le'='NETTLE'
Can you help me to learn more?
(Other definitions for nettle that I've seen before include "Growing" , "Sting or annoy with the plant" , "Upset" , "Plant with stinging hairs" , "anger?" .)