Fear capital — restricted to a very short distance (8)
I believe the answer is:
angstrom
'a very short distance' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'fear capital restricted' is the wordplay.
'fear' becomes 'angst'.
'capital' becomes 'rome' (Rome is an example).
'restricted' means to remove the last letter (restricted can mean limited or reduced).
'rome' with its final letter taken away is 'rom'.
'angst'+'rom'='ANGSTROM'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for angstrom that I've seen before include "Unit of wavelength measurement" , "Wavelength produced" , "Very little space" , "0.0001 micron" , "Microscopic length unit" .)