This contains growth hormone for parts of the body (6)
I believe the answer is:
thighs
'parts of the body' is the definition.
(I've seen this before)
'this contains growth hormone' is the wordplay.
'contains' is an insertion indicator.
'growth hormone' becomes 'gh' (this could be a standard abbreviation which I don't know about).
'this' enclosing 'gh' is 'THIGHS'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for thighs that I've seen before include "Chicken pieces" , "Parts of the body" , "Upper leg parts" , "Parts of legs" , "They're between knees and hips" .)