Worry caused by a new form of tax (5)
I believe the answer is:
angst
'worry' is the definition.
(I've seen this before)
'a new form of tax' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'caused by' acts as a link.
Can you help me to learn more?
(Other definitions for angst that I've seen before include "feeling worried?" , "Horrible feeling" , "General feeling of dread" , "Profound feeling of anxiety or dread" , "Acute, but unspecific, feeling of anxiety" .)