One day participating in contests brought back attachment to motorcycle (7)
I believe the answer is:
sidecar
'attachment to motorcycle' is the definition.
I can't tell whether this definition defines the answer.
'one day participating in contests brought back' is the wordplay.
'one' becomes 'i' (Roman numeral).
'day' becomes 'd' (abbreviation for day).
'participating in' is an insertion indicator.
'contests' becomes 'races' (race is a kind of contest).
'brought back' shows that the letters should be reversed in order.
'races' backwards is 'secar'.
'i'+'d'='id'
'id' going within 'secar' is 'SIDECAR'.
Can you help me to learn more?
(Other definitions for sidecar that I've seen before include "Low-slung two-wheeler" , "Cocktail of brandy, orange liqueur and lemon juice" , "Attachment to motor cycle" , "Attachment on motorcycle to carry passenger" , "Cocktail; bike attachment" .)