Bus one caught to follow child on horse (9)
I believe the answer is:
charabanc
'bus' is the definition.
(synonyms)
'one caught to follow child on horse' is the wordplay.
'one caught' becomes 'anc' (I can't explain this - if you can you should believe this answer much more).
'to follow' means one lot of letters go next to another (some letters go after or follow others).
'child' becomes 'ch' (abbreviation for child).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'horse' becomes 'Arab' (Arab is a type of horse).
'ch'+'arab'='charab'
'anc' put after 'charab' is 'CHARABANC'.
Can you help me to learn more?
(Other definitions for charabanc that I've seen before include "E.g. transport" , "Old tourist coach" , "Former coach" , "Old vehicle" , "Early coach" .)