Silly ducks on lake eaten by carp, perhaps (7)
I believe the answer is:
foolish
'silly' is the definition.
('foolish' can be similar in meaning to 'silly')
'ducks on lake eaten by carp perhaps' is the wordplay.
'ducks' becomes 'oo' (I've seen this in other clues).
'on' means one lot of letters go next to another.
'lake' becomes 'l'.
'eaten by' indicates putting letters inside.
'carp perhaps' becomes 'fish' (carp is a kind of fish).
'oo'+'l'='ool'
'ool' going within 'fish' is 'FOOLISH'.
(Other definitions for foolish that I've seen before include "Unwise or ridiculous" , "Absurd, not sensible" , "Imprudent" , "Idiotic" , "Silly, unwise" .)