Heat tea with iron (5)
I believe the answer is:
chafe
'heat' is the definition.
(thesaurus)
'tea with iron' is the wordplay.
'tea' becomes 'cha' (cha is a type of tea).
'with' is a charade indicator (letters next to each other).
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'cha'+'fe'='CHAFE'
(Other definitions for chafe that I've seen before include "Rub annoyingly" , "Become sore by rubbing" , "Fray" , "Rub, irritate" , "Make sore or warm by rubbing" .)