Decline to retire a little ill-affected (4)
I believe the answer is:
fall
'decline' is the definition.
('fall' can be a synonym of 'decline')
'retire a little ill-affected' is the wordplay.
'retire' says the letters should be written in reverse.
'a little' indicates a hidden word.
'llaf' can be found hidden inside 'ill affected'.
'llaf' backwards is 'FALL'.
'to' is the link.
(Other definitions for fall that I've seen before include "rain?" , "Autumn in the USA" , "Collapse; decline" , "What Americans call autumn" , "A season in the US" .)