Popular stage routine I have retired? (8)
I believe the answer is:
inactive
'retired?' is the definition.
('inactive' can be similar in meaning to 'retired')
'popular stage routine i have' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'stage routine' becomes 'act' (I can't explain this - if you can you should give a lot more credence to this answer).
'i have' becomes 'I've' (contraction of 'I have').
'in'+'act'+'ive'='INACTIVE'
Can you help me to learn more?
(Other definitions for inactive that I've seen before include "Still" , "lethargic" , "Not moving/working" , "Immobile, not working" , "Passive or idle" .)