Inform if Tony is out of sorts (6)
I believe the answer is:
notify
'inform' is the definition.
(notifying is a kind of informing)
'if tony is out of sorts' is the wordplay.
'is out of sorts' indicates an anagram.
'if'+'tony'='iftony'
'iftony' with letters rearranged gives 'NOTIFY'.
(Other definitions for notify that I've seen before include "Make known" , "Formally inform" , "Advise, apprise" , "alert" , "Send word" .)