In retrospect, Cummings initially should replace tungsten in pen, one not working (7)
I believe the answer is:
retiree
'in retrospect' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'cummings initially should replace tungsten in pen one not working' is the wordplay.
I cannot quite understand how this works, but
'cummings' could be 'ee' (poet EE Cummings) and 'ee' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for retiree that I've seen before include "One stopping work" , "Pensioner" , "One put out to pasture" , "Person out of work" , "Former American worker" .)