Dread memory becoming this short (8)
I believe the answer is:
angstrom
'this short' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'dread memory' is the wordplay.
'dread' becomes 'angst' (I've seen this in another clue).
'memory' becomes 'ROM' (ROM is an example).
'angst'+'rom'='ANGSTROM'
'becoming' 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" , "virtually no distance!" , "scientific unit" , "0.0001 micron" , "Unit in which light wavelengths are measured" .)