Principal notice inserted in border in front of flower (10)
I believe the answer is:
headmaster
'principal' is the definition.
(I know that principal can be written as headmaster)
'notice inserted in border in front of flower' is the wordplay.
'notice' becomes 'ad' (short for advert).
'inserted in' is an insertion indicator.
'border' becomes 'hem' (I've seen this before).
'in front of flower' becomes 'aster' (I can't justify this - if you can you should give a lot more credence to this answer).
'ad' placed into 'hem' is 'headm'.
'headm'+'aster'='HEADMASTER'
Can you help me to learn more?
(Other definitions for headmaster that I've seen before include "Top (male) teacher" , "Principal" , "School manager" .)