Another malfunction revealed to be heat-related (7)
I believe the answer is:
thermal
'be heat-related' is the definition.
(I've seen this in another clue)
'another malfunction revealed' is the wordplay.
'revealed' indicates a hidden word (I've seen 'reveal' mean this).
'THERMAL' is hidden in the letters of 'another malfunction'.
'to' acts as a link.
(Other definitions for thermal that I've seen before include "A lot of hot air" , "Up-current of air" , "Warm or hot - underwear?" , "Warm or hot, say air or spring" , "Concerned with high temperature" .)