Press chief penning note about poem in cipher (7)
I believe the answer is:
encoded
'in cipher' is the definition.
'press chief penning note about poem' is the wordplay.
'press chief' becomes 'ed' (I've seen this in other clues).
'penning' means one lot of letters goes inside another.
'note' becomes 'n' (abbreviation).
'about poem' becomes 'code' (I am not sure about this - if you are sure you should believe this answer much more).
'n'+'code'='ncode'
'ed' going around 'ncode' is 'ENCODED'.
(Other definitions for encoded that I've seen before include "as secrets are dispatched?" , "In cryptic version" , "Deed con (anag.)" , "formed in a difficult-to-understand way" .)