Remainder left in wing for a sport activity (9)
I believe the answer is:
wrestling
'sport activity' is the definition.
'wrestling' can be an answer for 'activity' (wrestling is a kind of activity). I'm not certain of the 'sport' bit.
'remainder left in wing' is the wordplay.
'remainder' becomes 'rest' (synonyms).
'left' becomes 'l' (common abbreviation).
'in' indicates putting letters inside.
'rest'+'l'='restl'
'restl' put inside 'wing' is 'WRESTLING'.
'for a' is the link.
Can you help me to learn more?
(Other definitions for wrestling that I've seen before include "gripping contest" , "Hand-to-hand grappling" , "Hand-to-hand combat" , "event" , "Graeco-Roman and freestyle Olympic events" .)