Light in attic, and leaky! (6)
I believe the answer is:
candle
'light' is the definition.
(candle is a kind of light)
'in attic and leaky' is the wordplay.
'in' says the answer is hidden in the clue.
'CANDLE' is hidden in the letters of 'attic and leaky'.
(Other definitions for candle that I've seen before include "Lanced in light" , "Means of illumination" , "something wicked" , "Symbol of hope" , "Wicked light" .)