Like singular old records (4)
I believe the answer is:
mono
'records' is the definition.
Although both the answer and definition are nouns, they are not in the same form of the noun.
'like singular old' is the wordplay.
'like singular' becomes 'mon' (I can't justify this - if you can you should believe this answer much more).
'old' becomes 'o' (abbreviation).
'mon'+'o'='MONO'
Can you help me to learn more?
(Other definitions for mono that I've seen before include "Single-channel sound" , "Transmitting over one channel" , "Single-speaker sound" , "Not stereo" .)