The boss, heated after losing a couple of letters? (4)
I believe the answer is:
head
'the boss' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for head that I've seen before include "Noggin" , "School boss" , "Leader; water pressure" , "Be in charge of; (come to) crisis" , "bean" .)