It's put aside when retiring (8)
I believe the answer is:
reserved
'retiring' is the definition.
(I've seen this before)
'it's put aside when' is the wordplay.
I cannot quite see how this works, but
'it's' could be 'es' ('e' can mean 'electronic' which is similar to 'IT') and 'es' is located in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for reserved that I've seen before include "Booked, being unemotional" , "unforthcoming" , "without emotion" , "cool" , "Booked - reticent" .)