Deal with rant I dismissed (5)
I believe the answer is:
trade
'deal with' is the definition.
(thesaurus)
'rant i dismissed' is the wordplay.
'rant' becomes 'tirade' (both can mean an angry outburst).
'dismissed' indicates named letters should be taken away.
'tirade' with 'i' taken away is 'TRADE'.
(Other definitions for trade that I've seen before include "Buying/selling of goods" , "Deal commercially" , "Dealings, business" , "Barter or swap" , "Commercial dealings" .)