Bit of publicity that leads to nothing but trouble (3)
I believe the answer is:
ado
'trouble' is the definition.
(both can mean bother or commotion)
'bit of publicity that leads to nothing' is the wordplay.
I cannot quite see how this works, but
'bit' could be 'o' (resembles 0, a binary digit or bit) and 'o' is located in the answer.
'publicity' could be 'ad' (short for advert) and 'ad' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'but' acts as a link.
Can you help me to learn more?
(Other definitions for ado that I've seen before include "stew is provided" , "'Much ... About Nothing, Shakespeare play (3)'" , "puff ball!" , "stir" , "Fuss, trouble" .)