More safe crackers triggering alarm? (8)
I believe the answer is:
fearsome
'triggering alarm?' is the definition.
(creating fear or alarm)
'more safe crackers' is the wordplay.
'crackers' indicates anagramming the letters (informal term for mad).
'more'+'safe'='moresafe'
'moresafe' anagrammed gives 'FEARSOME'.
(Other definitions for fearsome that I've seen before include "Frightening, terrible" , "Of frightening appearance" , "Frightful" , "Fame rose and became frightening" , "Dreadful" .)