Small duck seen twice not great (2-2)
I believe the answer is:
so-so
'not great' is the definition.
I can't tell whether this defines the answer.
'small duck seen twice' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'seen twice' says to double the letters.
's'+'o'='so'
'so' duplicated is 'SO-SO'.
Can you help me to learn more?
(Other definitions for so-so that I've seen before include "'Passable, middling (2-2)'" , "just about adequate" , "Fair to middling" , "Indifferently good" , "Rather middling" .)