Be up for bad deeds? (4)
I believe the answer is:
evil
'bad deeds?' is the definition.
(I've seen this in another clue)
'be up' is the wordplay.
'be' becomes 'live' (to be is to live or exist).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'live' in reverse letter order is 'EVIL'.
'for' is the link.
(Other definitions for evil that I've seen before include "Nefarious" , "Morally wrong" , "very naughty" , "Satanic" , "no good in this puzzle" .)