Only a personal impression but admissible as evidence (11)
I believe the answer is:
fingerprint
'evidence' is the definition.
(fingerprint is a kind of evidence)
'only a personal impression but admissible as' is the wordplay.
I cannot quite understand how this works, but
'impression' could be 'print' (impression created by a printer) and 'print' is present in the answer.
'as' could be 'in' (I've seen this in other clues) and 'in' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for fingerprint that I've seen before include "Dab" , "means of identification" , "Mark left by handler" .)