In high definition, I study the unknown (6)
I believe the answer is:
hidden
'the unknown' is the definition.
(thesaurus)
'in high definition i study' is the wordplay.
'in' means one lot of letters goes inside another.
'high definition' becomes 'hd' (this could be a standard abbreviation which I don't know about).
'study' becomes 'den' (term for a study or office).
'hd' placed around 'i' is 'hid'.
'hid'+'den'='HIDDEN'
Can you help me to learn more?
(Other definitions for hidden that I've seen before include "Deliberately placed out of sight and hard to find" , "Obscure" , "Covert, obscured" , "Concealed, recondite" , "Consealed or secret" .)