Stop bad mood risk (8)
I believe the answer is:
endanger
'risk' is the definition.
(to risk is to put in danger)
'stop bad mood' is the wordplay.
'stop' becomes 'end' (synonyms).
'bad mood' becomes 'anger' (I am not sure about this - if you are sure you should believe this answer much more).
'end'+'anger'='ENDANGER'
Can you help me to learn more?
(Other definitions for endanger that I've seen before include "Put someone at risk" , "Pose a threat to" , "Threaten" , "Put in harm's way" , "Place into peril, jeopardise" .)