What may go on after retiring in close game (7)
I believe the answer is:
nightie
'what may go on after retiring' is the definition.
(something worn after going to bed)
'close game' is the wordplay.
'close' becomes 'nigh' (similar in meaning).
'game' becomes 'tie' (I've seen this before).
'nigh'+'tie'='NIGHTIE'
'in' is the link.
(Other definitions for nightie that I've seen before include "Loose dress worn in bed" , "Female bedwear" , "Bedtime attire" , "one put on after dark" , "Female article of clothing" .)