For advice, it's up to the party leader (3)
I believe the answer is:
tip
'for advice' is the definition.
(a tip is a piece of advice)
'it's up to the party leader' is the wordplay.
'it's' becomes 'it' (I can't justify this - if you can you should believe this answer much more).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'to the party leader' becomes 'p' (leader of the word 'party').
'it' reversed gives 'ti'.
'ti'+'p'='TIP'
Can you help me to learn more?
(Other definitions for tip that I've seen before include "Empty" , "Piece of useful advice" , "Helpful suggestion" , "Clue" , "offered at end of repast" .)