Some task important to pass over lightly (4)
I believe the answer is:
skim
'pass over lightly' is the definition.
(I've seen this before)
'some task important to' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'SKIM' can be found hidden inside 'task important to'.
(Other definitions for skim that I've seen before include "Remove top (of milk)" , "Read cursorily" , "Remove surface layer" , "Remove top layer; read bits of" , "Brush over" .)