You and I have nothing but grief (3)
I believe the answer is:
woe
'grief' is the definition.
(I've seen this in another clue)
'you and i have nothing' is the wordplay.
'you and i' becomes 'we'.
'have' indicates putting letters inside.
'nothing' becomes 'o' (looks like zero - 0).
'we' going around 'o' is 'WOE'.
'but' is the link.
(Other definitions for woe that I've seen before include "Misery - tribulation" , "Archaic sorrow or grief" , "Great sorrow, distress" , "Misery, great suffering" , "Difficulty" .)