The lot will add up to a quid (5)
I believe the answer is:
total
'quid' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'the lot will add up to a' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'a' is present in the answer.
an anagram of 'lot' is 'otl' which is located in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for total that I've seen before include "Complete sum" , "Final tally" , "Whole, complete" , "final answer" , "Count" .)