Being informal, she's less rude! (8)
I believe the answer is:
gertrude
'being informal she's' is the definition.
I can't tell whether this definition defines the answer.
'less rude' is the wordplay.
'less' becomes 'gert' (I can't explain this - if you can you should believe this answer much more).
'gert'+'rude'='GERTRUDE'
Can you help me to learn more?
(Other definitions for gertrude that I've seen before include "Hamlet's mother; drug tree (anag.)" , "queen" .)