Can be sickly after onset of jaundice (4)
I believe the answer is:
jail
'can' is the definition.
(The Can is slang for prison)
'sickly after onset of jaundice' is the wordplay.
'sickly' becomes 'ail' (I've seen this in other clues**).
'after' is a charade indicator (letters next to each other).
'onset of' says to take the initial letters.
The first letter of 'jaundice' is 'j'.
'ail' after 'j' is 'JAIL'.
'be' acts as a link.
(Other definitions for jail that I've seen before include "sentence" , "Gaol" , "having a stretch here?" , "detention" , "place for punishment" .)