He took a taxi back and forth (5)
I believe the answer is:
bacon
'he took a' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'taxi back and forth' is the wordplay.
'taxi' becomes 'cab' (synonyms).
'back' says the letters should be written backwards.
'and' is a charade indicator (letters next to each other).
'forth' becomes 'on' (I can't justify this - if you can you should give a lot more credence to this answer).
'cab' reversed gives 'bac'.
'bac'+'on'='BACON'
Can you help me to learn more?
(Other definitions for bacon that I've seen before include "Francis -, twentieth century Ir. artist" , "Breakfast meat?" , "successfully brought home" , "Breakfast food" , "Cut of pork" .)