Silly daughter getting behind (4)
I believe the answer is:
daft
'silly' is the definition.
(I've seen this before)
'daughter getting behind' is the wordplay.
'daughter' becomes 'd'.
'getting' is a charade indicator (letters next to each other).
'behind' becomes 'aft' ('aft' can be a synonym of 'behind').
'd'+'aft'='DAFT'
(Other definitions for daft that I've seen before include "like a brush?" , "'Silly, foolish (4)'" , "Informally silly or crazy" , "Barmy, crackers" , "Half-witted" .)