Fake coach has to go wrong (5)
I believe the answer is:
bogus
'fake' is the definition.
(I know that fake can be written as bogus)
'coach has to go wrong' is the wordplay.
'coach' becomes 'bus' (synonyms).
'has' is an insertion indicator.
'to go wrong' becomes 'og' (I can't justify this - if you can you should believe this answer much more).
'bus' enclosing 'og' is 'BOGUS'.
Can you help me to learn more?
(Other definitions for bogus that I've seen before include "Mock" , "Pretended" , "Fictitious" , "Phoney, not genuine" , "taking one for a ride?" .)