Being informal, she's less rude! (8)

I believe the answer is:

gertrude

I'm a little stuck... Click here to teach me more about this clue!

'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" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app