A part of working? That's being cool-headed! (2,2)
I believe the answer is:
in on
'a part of' is the definition.
(I've seen this in another clue)
'working? that's being cool-headed' is the wordplay.
I cannot quite see how this works, but
'working?' could be 'on' (e.g. a machine is working or on) and 'on' is present in the answer.
'cool' could be 'in' ('in' can mean fashionable or cool) and 'in' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for in on that I've seen before include "Wise to" , "Participating in - knowing about" , "Sharing with" , "Aware of - being part of" , "Aware of secret" .)