Hormone abuse with temperature dropping at home (7)
I believe the answer is:
insulin
'hormone' is the definition.
(insulin is a kind of hormone)
'abuse with temperature dropping at home' is the wordplay.
I cannot quite see how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is found in the answer.
'home' could be 'in' ('he's home' can mean 'he's in') and 'in' is present in the answer.
This explanation may well be incorrect...
(Other definitions for insulin that I've seen before include "Hormone involved in diabetes" , "Hormone secreted by the pancreas" , "It regulates glucose in the blood" , "Regulator of blood sugar" , "Hormone produced in the pancreas to control body sugar" .)