Generally she’s not beastly! (5)
I believe the answer is:
flora
'not beastly' is the definition.
I can't tell whether this definition defines the answer.
'generally she's' is the wordplay.
'generally' becomes 'fl' (I can't justify this - if you can you should believe this answer much more).
'she' becomes 'ora'.
'fl'+'ora'='FLORA'
Can you help me to learn more?
(Other definitions for flora that I've seen before include "growing flowers" , "local plants" , "Plant life (to go with fauna)" , "For example, Miss Macdonald" , "growing things" .)