Origin of many a clue recycled every year? It's my fault (3,5)
I believe the answer is:
mea culpa
'it's my fault' is the definition.
(I've seen this before)
'origin of many a clue recycled every year?' is the wordplay.
'origin of' indicates taking the first letters.
'recycled' indicates anagramming the letters.
'every year?' becomes 'pa' (per annum).
The initial letter of 'many' is 'm'.
'a'+'clue'='aclue'
'aclue' is an anagram of 'eacul'.
'm'+'eacul'+'pa'='MEA CULPA'
(Other definitions for mea culpa that I've seen before include "Total admission of one's guilt (Latin)" , "Admission of fault" , "Acknowledgement of one's own fault (Latin)" , "I'm guilty (Latin)" , "Acknowledgment of error or guilt" .)