Difficult, and it's no good going by taxi (6)
I believe the answer is:
taxing
'difficult' is the definition.
(I've seen this in another clue)
'it's no good going by taxi' is the wordplay.
'it's no good' becomes 'ng' (abbreviation).
'going by' means one lot of letters go next to another.
'ng' put after 'taxi' is 'TAXING'.
'and' acts as a link.
(Other definitions for taxing that I've seen before include "Physically or mentally demanding" , "Making heavy demands, like Revenue Commissioners" , "Onerous" , "Making great demands" , "'Not easily borne, very wearing (6)'" .)