Old-fashioned computing aid to record sound of a cadence (9)
I believe the answer is:
logarithm
'old-fashioned' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'computing aid to record sound of a cadence' is the wordplay.
I cannot really see how this works, but
'computing' could be 'it' (IT is an abbreviation for Information Technology) and 'it' is present in the answer.
'record' could be 'log' (logging is a kind of recording) and 'log' is found within the answer.
'a' is within 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 logarithm that I've seen before include "It undoes power" , "Mathematical aid simplifying multiplication and division - a girl moth (anag)" , "Aid to mathematical calculation" , "Exponent" , "Power to which base number must be raised to obtain a given number" .)