I concur with this senior citizen, funnily - there's plenty here (10)
I believe the answer is:
cornucopia
'this senior citizen funnily there's plenty here' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'i concur' is the wordplay.
I cannot really understand how this works, but
'i' could be 'a' and 'a' is found in the answer.
an anagram of 'concur' is 'cornuc' which is within the answer.
This may be the basis of the clue (or it may be nonsense).
'with' acts as a link.
Can you help me to learn more?
(Other definitions for cornucopia that I've seen before include "Wealth" , "There's plenty here!" , "Abundant supply of good things" , "Horn of plenty" , "Great abundance" .)