Duck, swan, not decided yet? (4)
I believe the answer is:
open
'decided yet?' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can occasionally define each other.
'duck swan' is the wordplay.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'swan' becomes 'pen' (pen is a kind of swan).
'o'+'pen'='OPEN'
'not' acts as a link.
Can you help me to learn more?
(Other definitions for open that I've seen before include "Unenclosed" , "Not enclosed" , "Eager to receive" , "'Frank, not secret (4)'" , "Frank; unobstructed" .)