Admirers of cooling systems (4)
I believe the answer is:
fans
'admirers' is the definition.
(fan is a kind of admirer)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for fans that I've seen before include "Devotees" , "Supporters" , "Enthusiasts" , "Aficionados" , "Devices for creating currents of air" .)