I'd backed commercial vehicle into dais, creating obstacle (12)
I believe the answer is:
disadvantage
'obstacle' is the definition.
(thesaurus)
'i'd backed commercial vehicle into dais' is the wordplay.
'backed' shows that the letters should be reversed in order.
'commercial' becomes 'ad'.
'vehicle' becomes 'van' (van is a kind of vehicle).
'into' indicates putting letters inside.
'dais' becomes 'stage' (I've seen this before).
'id' reversed gives 'di'.
'ad'+'van'='advan'
'advan' placed inside 'stage' is 'sadvantage'.
'di'+'sadvantage'='DISADVANTAGE'
'creating' is the link.
(Other definitions for disadvantage that I've seen before include "Drawback" , "Catch" , "Flaw -- weak point" , "Hindrance" , "Downside" .)