Ten or so forms in biochemical compound (9)
I believe the answer is:
serotonin
'biochemical compound' is the definition.
'serotonin' can be an answer for 'compound' (serotonin is a kind of compound). I am not sure about the 'biochemical' bit.
'ten or so forms in' is the wordplay.
'forms' indicates anagramming the letters.
'ten'+'or'+'so'='tenorso'
'tenorso' anagrammed gives 'seroton'.
'seroton'+'in'='SEROTONIN'
Can you help me to learn more?
(Other definitions for serotonin that I've seen before include "Neurotransmitter hormone, involved in depression say" , "Compound acting as a neurotransmitter" , "Compound in the blood affecting sleep and depression - soon inert (anag)" , "Compound in brain" , "Compound present in serum - ironstone (anag)" .)