Uncertain about notice that's dodgy (5)
I believe the answer is:
shady
'dodgy' is the definition.
(I know that dodgy can be written as shady)
'uncertain about notice' is the wordplay.
'uncertain' becomes 'shy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'about' is an insertion indicator.
'notice' becomes 'ad' (both can mean an advertisement).
'shy' enclosing 'ad' is 'SHADY'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for shady that I've seen before include "underhand" , "Of dubious legality" , "Disreputable -- out of the sun" , "Dubious (of character)" , "Questionably legal" .)