Not one of them is worth a dollar! (5)
I believe the answer is:
cents
'them is worth a dollar' is the definition.
I can't tell whether this defines the answer.
'not one' is the wordplay.
I cannot quite understand how this works, but
'not' could be 'nt' (synonyms) and 'nt' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for cents that I've seen before include "US money, e.g." , "money abroad" , "American coins" , "Hundredths of dollar" , "Fractions of dollar" .)