Getting on for ninety perhaps? (9)
I believe the answer is:
euphemism
'getting' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for euphemism that I've seen before include "Inoffensive expression substituted for one that may be offensive" , "Milder substitute word" , "Word used instead of something more unpleasant" , "Inoffensive term used instead of an unpleasant one" , "Mild substitute for taboo word" .)