Girl with a Latin temper (6)
I believe the answer is:
anneal
'temper' is the definition.
('anneal' can be a synonym of 'temper')
'girl with a latin' is the wordplay.
'girl' becomes 'anne' (I've seen this before**).
'with' means one lot of letters go next to another.
'latin' becomes 'l'.
'anne'+'a'+'l'='ANNEAL'
(Other definitions for anneal that I've seen before include "Toughen by a process of gradually heating and cooling" , "Fire or glaze as in kiln" , "Temper, harden" , "Heat and cool slowly to toughen, metal or glass" , "Heat treat (metal/glass)" .)