Hear/see poem in secret language (4)
I believe the answer is:
code
'secret language' is the definition.
(I've seen this before)
'hearsee poem' is the wordplay.
'hearsee' becomes 'c' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'poem' becomes 'ode' (ode is a kind of poem).
'c'+'ode'='CODE'
'in' is the link.
Can you help me to learn more?
(Other definitions for code that I've seen before include "See 12" , "System of words arrangement for secrecy" , "Program instruction" , "Computer language, say" , "conventions" .)