Cause to explode (8)
'cause to explode' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for detonate that I've seen before include "Trigger" , "Cause to explode" , "go off with a bang" , "Start 15 [EXPLOSION]" , "Discharge" .)
(Other definitions for set off that I've seen before include "Leave - explode" , "Explode; start journey" , "'Leave on a journey (3,3)'" , "Display - mount - start journey" , "radio with no reception" .)