Chaucer's first poem needs deciphering (4)
I believe the answer is:
code
'needs deciphering' is the definition.
I can't judge whether this defines the answer.
'chaucer's first poem' is the wordplay.
'chaucer's first' becomes 'c' (ost letter of 'chaucer').
'poem' becomes 'ode' (ode is a kind of poem).
'c'+'ode'='CODE'
Can you help me to learn more?
(Other definitions for code that I've seen before include "difficult to read" , "See 21 Across" , "Ethical standards" , "Method of secret communication" , "Eg, Morse" .)