Catch sight of naughty kid cutting legs off (7)
I believe the answer is:
glimpse
'catch sight of' is the definition.
(I've seen this before)
'naughty kid cutting legs off' is the wordplay.
'naughty kid' becomes 'imp' (imp can mean a misbehaving child).
'cutting' means one lot of letters goes inside another (some letters cut their way into a word).
'off' indicates anagramming the letters.
'legs' with letters rearranged gives 'glse'.
'imp' going within 'glse' is 'GLIMPSE'.
(Other definitions for glimpse that I've seen before include "Catch brief sight of" , "Notice" , "Peek" , "Quick view" , "Briefly catch sight of" .)