Where one rides a rollercoaster? Just stop from flying off (10)
I believe the answer is:
fairground
'where one rides a rollercoaster?' is the definition.
(a fairground might have rollercoasters)
'just stop from flying off' is the wordplay.
'just' becomes 'fair' (just can mean fair in the sense of showing justice).
'stop from flying off' becomes 'ground' (ground can mean to keep on the ground).
'fair'+'ground'='FAIRGROUND'
(Other definitions for fairground that I've seen before include "Entertainment centre" , "Where one plays" , "Scary ride here perhaps" , "good enough for entertainment" , "Entertainment venue" .)