Upset president involved in underworld contract (9)
I believe the answer is:
displease
'upset' is the definition.
(thesaurus)
'president involved in underworld contract' is the wordplay.
'president' becomes 'p' (common abbreviation eg in VP).
'involved in' is an insertion indicator.
'underworld' becomes 'dis' (underworld in classical mythology).
'contract' becomes 'lease' (leasing is a kind of contracting).
'dis'+'lease'='dislease'
'p' put within 'dislease' is 'DISPLEASE'.
(Other definitions for displease that I've seen before include "Nettle" , "Vex" , "Aggravate" , "Anger" , "Upset" .)