Sham coach has to go wrong (5)
I believe the answer is:
bogus
'sham' is the definition.
(thesaurus)
'coach has to go wrong' is the wordplay.
'coach' becomes 'bus' ('bus' can be a synonym of 'coach').
'has' means one lot of letters goes inside another.
'to go wrong' becomes 'og' (I can't explain this - if you can you should believe this answer much more).
'bus' going around 'og' is 'BOGUS'.
Can you help me to learn more?
(Other definitions for bogus that I've seen before include "Not genuine, sham" , "Sham, counterfeit" , "Sham, false" , "Not true" , "taking one for a ride?" .)