Call for hostilities with tirade (7)
I believe the answer is:
warrant
'call for' is the definition.
(I've seen this before)
'hostilities with tirade' is the wordplay.
'hostilities' becomes 'war' (hostilities between nations).
'with' says to put letters next to each other.
'tirade' becomes 'rant' (both can mean an angry outburst).
'war'+'rant'='WARRANT'
(Other definitions for warrant that I've seen before include "Permit for arrest, search of premises, etc" , "Writ for arrest" , "Call for" , "Guarantee" , "Merit, justify" .)