Oddie's first swan not ringed? (4)
I believe the answer is:
open
'not ringed?' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs sometimes define each other.
'oddie's first swan' is the wordplay.
'oddie's first' becomes 'o' (1st letter of 'oddie').
'swan' becomes 'pen' (pen is a kind of swan).
'o'+'pen'='OPEN'
Can you help me to learn more?
(Other definitions for open that I've seen before include "Allowing access" , "Candid - ready for business" , "Contest that includes all comers" , "Unenclosed" , "Not shut up or hidden" .)