Soup rejuvenated her at two (3,5)
I believe the answer is:
hot water
'soup' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I can't see?
'rejuvenated her at two' is the wordplay.
'rejuvenated' indicates anagramming the letters (I've seen this in other clues).
'her'+'at'+'two'='herattwo'
'herattwo' is an anagram of 'HOT WATER'.
Can you help me to learn more?
(Other definitions for hot water that I've seen before include "Taps contents" , "Trouble (if you're in it)" , "Uncomfortable predicament to be in?" , "that comes at bath time?" , "(Liquid) trouble!" .)