Notice lids put back (4)
I believe the answer is:
spot
'notice' is the definition.
(spot can mean to notice or observe)
'lids put back' is the wordplay.
'lids' becomes 'tops' (I've seen this in another clue).
'put back' shows that the letters should be reversed in order.
'tops' written backwards gives 'SPOT'.
(Other definitions for spot that I've seen before include "Espy; mark" , "Observe - place" , "Notice - stain - pick out" , "Fix" , "make out" .)