Hormone? My mood is being restricted (9)
I believe the answer is:
cortisone
'hormone?' is the definition.
(I know that cortisone is a type of adrenal cortical steroid)
'my mood is being restricted' is the wordplay.
'my' becomes 'cor' (both are expressions of surprise).
'mood' becomes 'tone' (tone is a kind of mood).
'being restricted' is an insertion indicator.
'tone' going around 'is' is 'tisone'.
'cor'+'tisone'='CORTISONE'
(Other definitions for cortisone that I've seen before include "hormone used in medicine!" , "Steroid" , "anti-inflammatory one" , "Drug" .)