Flatter bloomer, less cooked on top (6,2)
I believe the answer is:
butter up
'flatter' is the definition.
(buttering up is a kind of flattering)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for butter up that I've seen before include "Flatter to obtain favour" , "Flatter using common dairy product" , "like 17 [SWEET TALK]" , "Soft-soap" , "mountain goat?" .)