Unusual case passed on to up the intensity (8)
I believe the answer is:
escalate
'up the intensity' is the definition.
'escalate' can be an answer for 'up' (thesaurus). I am not sure about the 'the intensity' bit.
'unusual case passed on' is the wordplay.
'unusual' indicates an anagram.
'passed on' becomes 'late' (both can mean dead).
'case' with letters rearranged gives 'esca'.
'esca'+'late'='ESCALATE'
'to' is the link.
Can you help me to learn more?
(Other definitions for escalate that I've seen before include "Ramp up" , "rocket" , "Snowball" , "Increase in intensity or extent, like trouble brewing" , "Amplify" .)