Lie about short term mediation (12)
I believe the answer is:
intervention
'mediation' is the definition.
(thesaurus)
'lie about short term' is the wordplay.
'lie' becomes 'invention'.
'about' is an insertion indicator.
'short term' becomes 'ter' (I can't explain this - if you can you should believe this answer much more).
'invention' placed around 'ter' is 'INTERVENTION'.
Can you help me to learn more?
(Other definitions for intervention that I've seen before include "Mediation, stepping-in" , "Agency" , "Action taken to improve a medical disorder" , "Mediation; interference" .)