Boss in awful rage upon receiving fines (6)
I believe the answer is:
gaffer
'boss' is the definition.
(gaffer can informally mean a boss)
'awful rage upon receiving fines' is the wordplay.
'awful' is an anagram indicator.
'upon receiving' indicates putting letters inside.
'fines' becomes 'ff' (an abbreviation for fine written twice).
'rage' is an anagram of 'gaer'.
'gaer' going around 'ff' is 'GAFFER'.
'in' acts as a link.
(Other definitions for gaffer that I've seen before include "Senior electrician on a film/TV set" , "Chief electrician on a film set" , "Superior" , "Old man" , "blunderer" .)