Festival month sees indefinite number succumbing to ill temper (7)
I believe the answer is:
jubilee
'festival' is the definition.
The answer and definition can be both related to time as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for jubilee that I've seen before include "that could be silver or gold?" , "Clip, say" , "SECOND PART OF 15" , "Sort of clip" , "period of rejoicing" .)