Bossily, he gives a chap a shouted warning (7)
I believe the answer is:
foreman
'bossily he gives a chap a shouted warning' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'bossily he' is the wordplay.
'bossily' becomes 'fore' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'he' becomes 'man' (I've seen this in another clue).
'fore'+'man'='FOREMAN'
Can you help me to learn more?
(Other definitions for foreman that I've seen before include "Supervising worker" , "Male supervisor" , "Fellow in charge" , "Charge hand" , "spokesman" .)