Tree had exploded in an Arnie movie! (3,4)
I believe the answer is:
red heat
'an arnie movie' is the definition.
I can't tell whether this defines the answer.
'tree had exploded' is the wordplay.
'exploded' indicates anagramming the letters.
'tree'+'had'='treehad'
'treehad' anagrammed gives 'RED HEAT'.
'in' is the link.
Can you help me to learn more?
(Other definitions for red heat that I've seen before include "High temperature" , "Temperature at which something glows" , "Fieriness" , "Glowing temperature" .)