Praise ace with 250 — ace Izetti is! (7)
I believe the answer is:
acclaim
'praise' is the definition.
(I've seen this before)
'ace with 250 ace izetti is' is the wordplay.
'ace' becomes 'a' (abbreviation).
'with' means one lot of letters go next to another.
'c50' becomes 'ccl' (I can't justify this - if you can you should give a lot more credence to this answer).
'ace' becomes 'a' (abbreviation).
'izetti is' becomes 'I'm' (where the crossword setter is 'Izetti').
'a'+'ccl'+'a'+'im'='ACCLAIM'
Can you help me to learn more?
(Other definitions for acclaim that I've seen before include "Enthusiastic and public praise" , "Welcome with shouts of applause" , "Laud" , "Plaudits" , "Declare" .)