Flavouring substance in vehicle, one everybody rejected (7)
I believe the answer is:
vanilla
'flavouring substance' is the definition.
'vanilla' can be an answer for 'flavouring' (I've seen this before). I'm not certain of the 'substance' bit.
'vehicle one everybody rejected' is the wordplay.
'vehicle' becomes 'van' (van is a kind of vehicle).
'one' becomes 'i' (Roman numeral).
'everybody' becomes 'all' (I've seen this before).
'rejected' is a reversal indicator.
'all' reversed gives 'lla'.
'van'+'i'+'lla'='VANILLA'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for vanilla that I've seen before include "Flavouring derived from an orchid" , "type of orchid" , "Commonplace - flavouring" , "Common flavour for ices" , "Popular ice-cream, flavour" .)