As a personal impression there's nothing quite like it (11)
I believe the answer is:
fingerprint
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'as a personal impression there's nothing quite' is the wordplay.
I cannot really see how this works, but
'as' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
'impression' could be 'print' (impression created by a printer) and 'print' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'like' acts as a link.
Can you help me to learn more?
(Other definitions for fingerprint that I've seen before include "means of identification" , "Dab" , "Mark left by handler" .)