A bit of sauce - just over half a pound? (3)
I believe the answer is:
lip
'a bit of sauce' is the definition.
(I've seen this in another clue)
'over half a pound?' is the wordplay.
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'half a' becomes 'ip' (I can't explain this - if you can you should give a lot more credence to this answer).
'pound?' becomes 'L' (abbreviation e.g. Lsd - pounds, shillings, pence).
'ip' put after 'l' is 'LIP'.
'just' is the link.
Can you help me to learn more?
(Other definitions for lip that I've seen before include "Fleshy fold of mouth tissue" , "Edge of mouth" , "Edge; impudent talk" , "giving such insincere service" , "Rim of an orifice" .)