Set off at ten with doe in need of treatment (8)
I believe the answer is:
detonate
'set off' is the definition.
(synonyms)
'at ten with doe in need of treatment' is the wordplay.
'with' says to put letters next to each other.
'in need of treatment' indicates anagramming the letters.
'at'+'ten'+'doe'='attendoe'
'attendoe' is an anagram of 'DETONATE'.
(Other definitions for detonate that I've seen before include "Cause to explode" , "Set off explosive device" , "Trigger" , "Start 15 [EXPLOSION]" , "Blow up, explode" .)