Mad race to run atomic device (7)
I believe the answer is:
reactor
'atomic device' is the definition.
'reactor' can be an answer for 'device' (reactor is a kind of device). I am unsure of the 'atomic' bit.
'mad race to run' is the wordplay.
'mad' indicates anagramming the letters.
'run' becomes 'r' (cricket abbreviation).
'race'+'to'='raceto'
'raceto' anagrammed gives 'reacto'.
'reacto'+'r'='REACTOR'
Can you help me to learn more?
(Other definitions for reactor that I've seen before include "source of power, perhaps" , "device for generating energy" , "Nuclear power station core" , "See 3 Down" , "Apparatus for production of nuclear energy" .)