Initially confused by poem in secret language (4)
I believe the answer is:
code
'secret language' is the definition.
(I've seen this before)
'initially confused by poem' is the wordplay.
'initially' suggests taking the first letters.
'by' says to put letters next to each other.
'poem' becomes 'ode' (ode is a type of poem).
The initial letter of 'confused' is 'c'.
'c'+'ode'='CODE'
'in' is the link.
(Other definitions for code that I've seen before include "regulations" , "System of words arrangement for secrecy" , "Morse is a good example" , "Secret symbols" , "Secret system of letters. words etc" .)