"The fellow in the white hat", I put in, "is the boss" (5)
I believe the answer is:
chief
'the boss' is the definition.
(synonyms)
'the fellow in the white hat i put in' is the wordplay.
'the fellow' becomes 'he' (he refers to a man).
'in the' indicates putting letters inside.
'white hat' becomes 'cf' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'put in' indicates putting letters inside.
'he' placed within 'cf' is 'chef'.
'chef' placed around 'i' is 'CHIEF'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for chief that I've seen before include "Head of a native American tribe" , "Person in charge, head" , "Tribal head" , "Organisation head" , "Ordinary type" .)