A valued piece of sticky paper (5)
I believe the answer is:
stamp
'paper' is the definition.
(I know that stamp is a type of piece of paper)
'a valued piece of sticky' is the wordplay.
I cannot really see how this works, but
'a' could be 'amp' (A is the symbol for the amp or ampere) and 'amp' is present in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stamp that I've seen before include "Postal label" , "cast?" , "contributions?" , "Imprint, brand" , "Tread noisily" .)