Trauma with schoolteacher mislaying note (6)
I believe the answer is:
stress
'trauma' is the definition.
(thesaurus)
'schoolteacher mislaying note' is the wordplay.
'schoolteacher' becomes 'mistress' (old-fashioned term for a female school teacher).
'mislaying' is a deletion indicator.
'note' becomes 'mi' (as in 'do re mi').
'mistress' with 'mi' taken out is 'STRESS'.
'with' acts as a link.
(Other definitions for stress that I've seen before include "Cause of crack" , "Tension, pressure" , "'Strain, tension (6)'" , "Feeling of pressure" , "Force" .)