Light meal: live without it (4)
I believe the answer is:
bite
'light meal' is the definition.
(I've seen this before)
'live without it' is the wordplay.
'live' becomes 'be' (synonyms).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'be' enclosing 'it' is 'BITE'.
(Other definitions for bite that I've seen before include "Snake or insect wound" , "Punch" , "Clamp down teeth" , "Mouthful" , "Light meal" .)